Chlorosis and browning

[Muarco]

Hi there, my plant seems to be experiencing some issues. I believe the cause to be a Potassium deficiency but I would like to hear a second opinion before risking some more damage.
Plant is a Jack Herrer Auto 14 weeks old. Been feeding nutes 2 times a week and plain water once a week. Feeding pH is around 6.3-6.5 and ppm around 500 to 800. I measured runoff yesterday and pH was 6.5 while ppm 1800.
The plant seems to be yellowing on the top leaves. Starting from the tip toward the center with some leaves showing some brown dots and patches. They eventually dry up and become crunchy. Also some bottom leaves are affected but if I remember correctly it started from the top. Been feeding a 4ml/l of Plagron Terra Bloom and using CalMag every once in a while. Watering every 2-3 days with 3l the 15l pot. Room temperatures are 27° during day and 21° at night. RH in between 45% in the day to a 60% peak at night.
Using an HPS 400W raised at 40cm from the canopy.

I think the problem might be some salt buildup and some nutrients lockout but as I said I would like to hear a second opinion.

Thanks in advance

 

[TanzanianMagic]

It is potassium deficiency/lockout.

You should check out what the runoff is, because the EC is likely too high and the pH too low.

Also, you should look into pruning some of those leaves for airflow.

Pot size - think 1 gallon per foot of expected growth, and you should transplant them into pots at least twice 11 liters, into a non-fertilized soil with lots of perlite, so the roots can't burn and shock the flowering plants.

Also, you're likely feeding and watering too often, as well as too much, because of the small pot size.

 

[Muarco]

It is potassium deficiency/lockout.

You should check out what the runoff is, because the EC is likely too high and the pH too low.

Also, you should look into pruning some of those leaves for airflow.

Pot size - think 1 gallon per foot of expected growth, and you should transplant them into pots at least twice 11 liters, into a non-fertilized soil with lots of perlite, so the roots can't burn and shock the flowering plants.

Also, you're likely feeding and watering too often, as well as too much, because of the small pot size.

Thanks for the input, I had to correct pot size since it was 15l and not 11l so that's around 4 gallons. I'm also quite sure about watering since I always check the pot for weight and most of the time after 3 days I can feel the soil dried up almost completely so that's why I try watering on 2nd days when the soil is still a bit moist. I've only flushed her once 2 weeks ago when this problem started showing and seen no improvements. So I went the other way and feed her 1/2 recommended dose and now slowly going up. But she didn't improve so now I'm wondering if I should flush again with Flora Kleen or just stop feeding nutes?

 

[Muarco]

That's when the first issues came up. Almost 4 weeks ago.

 

[Muarco]

.

 

[TanzanianMagic]

Thanks for the input, I had to correct pot size since it was 15l and not 11l so that's around 4 gallons. I'm also quite sure about watering since I always check the pot for weight and most of the time after 3 days I can feel the soil dried up almost completely so that's why I try watering on 2nd days when the soil is still a bit moist. I've only flushed her once 2 weeks ago when this problem started showing and seen no improvements. So I went the other way and feed her 1/2 recommended dose and now slowly going up. But she didn't improve so now I'm wondering if I should flush again with Flora Kleen or just stop feeding nutes?

What was the EC of the runoff?

Also, even 15l is almost 4 gallons. Whenever the plant is way wider than the pot, the pot is likely too small. Also when repotting in light soil, only mix the light soil with magnesium lime and perlite.

There seems to be something going on at the root level.

 

[Muarco]

What was the EC of the runoff?

Also, even 15l is almost 4 gallons. Whenever the plant is way wider than the pot, the pot is likely too small. Also when repotting in light soil, only mix the light soil with magnesium lime and perlite.

There seems to be something going on at the root level.

It was reading around 300 millisiemens/centimeter [mS/cm] but it's the first time I'm using the TDS reader for measuring EC. I usually read the ppm measurement, which was 1600-1800ppm. I also agree on the roots as possible cause. I have clay pebbles at the bottom of the pot for drainage. Even been considering that they possibly influence pH but that wouldn't leave me with a runoff at 6.5pH. The soil I'm using is Plagron Light Mix. The lady was grown in the same pot from start to finish. I'm learning the importance of a bigger pot. Sadly the misconception is that autoflowers need smaller pots but while this might have been true in the past, now doesn't hold the same. With AF literally becoming as big as photoperiodic.

 

[TanzanianMagic]

I usually read the ppm measurement, which was 1600-1800ppm

Problem solved.

1800PPM is 2.6 EC on the EC to PPM Trunchon conversion chart.

https://www.canna-uk.com/sites/defa...lt/articles-electricalconductivity_text_0.png (try with http instead of the https which this website keeps changing the URL to)

That's at least 1 point too high. Bringing PPM back from 1800 to 1000 (1.6 EC) is a good start.

1800 PPM would be in EC:

Truncheon 2.6
Hanna 3.6
Eutech 2.8

They're in flowering, and they need some nutrients, however too many nutrients will start blocking out nutrients. It will also pull down the pH.

If you slowly flush the medium with a very low nutrient concentration (0.2 EC), and then give them 0.6 EC of bloom food and 0.1 EC of epsom salt, they'll be ok, minus a few leaves.

I have clay pebbles at the bottom of the pot for drainage. Even been considering that they possibly influence pH but that wouldn't leave me with a runoff at 6.5pH.

Clay pebbles buffer to 7.0, and should always be treated by putting them in a tub with water for at least a day, preferrably a week, so they can properly take up water and won't dehydrate small roots. The process is finished when you can no longer hear them absorbing water.

--

That's why I always like to use a combination of solid, slow release nutrients (supersoil) and a light concentration of bloom food (P) to stimulate root growth and strengthen the stem/branches (K). Liquid nutrients act fast for the immediate feeding, and solid nutrients act for a long time so nutrient deficiencies stay away.

The soil I'm using is Plagron Light Mix. The lady was grown in the same pot from start to finish. I'm learning the importance of a bigger pot. Sadly the misconception is that autoflowers need smaller pots but while this might have been true in the past, now doesn't hold the same. With AF literally becoming as big as photoperiodic.

- Light Mix

If used on it's own, it is always good to mix in a few tablespoons of magnesium lime, and a phophorus source like rock phosphate. I personally us it as a basis for mixing soils, because it contains no nutrients and it buffers it's pH too low. I would mix light mix, worm castings and perlite at 1/3 each. And use the same mix as the basis for a supersoil with alfalfa pellets (N, triacontanol, trace elements, protein), rock phosphate (P, Ca, trace elements), Vinasse (K, sugars), wood ash (K, trace elements), Maerl magnesium lime (Mg, Ca), silica clay like Mineral Magic (Si, trace elements), lava meal (trace elements), seaweed (trace elements, plant hormones). Plus 20% more perlite to keep the supersoil mix light and aerated.

That way, the microbes have all the nutrients the plants need, to work with - NPK, Ca Mg Si S, trace elements Fe, Cu, Zn, Mb, Mn, etc., as well as plant hormones, some calories from the alfalfa pellets and vinasse.

You can use any available nutrient source. The Rev's book True Living Organics is a great source for various nutrients. All organic nutrients are raw materials, which need to be processed by microbes.

You layer the grow rocks, then supersoil, then the standard mix on top, sprinkle with some oat flakes and sliced banana (calories for the microlife which makes everything move) and cover with some hemp bedding of 1/4 inch (carbon for the microlife).

I prefer using a pot with an inbuilt reservoir that the roots can grow into.

And then the only liquid nutrients are a light concentration of bloom food and epsom salt.

This stimulate root growth, strong stems and a healthy foliage, and all you do is top up the reservior until flowering starts.

 

[Muarco]

Big thanks for the extensive answer. I'm already working on adjusting the EC. I fed 3ml/l of Florakleen and now waiting to see some improvements.

I take the chance to ask about other two plants in the garden.

One seems to be affected by botrytis but I'm not sure because it could also be some leaves turning brown. Damage is in the middle of the plant right under the canopy

Wondering if I should cut or let it finish ripening.

Another plant is currently showing some burned pistils. I think it might be due to the fan blowing directly onto those buds almost 24/7 to help control the heat. Just scared it could be something worst like a fungus.