Stunted growth - a repeating problem I can not solve.

[plan500]

Dear fellow growers,

I need your help to figure out a problem with my plants that has been following me for the last 6 grows. I am running a mid-sized operation and It is a repeating problem that I just can’t seem to understand and resolve.

It all goes normal with the seedlings, they are growing well with a light color of the leaves and no visible problems. However, as I approach week 3 of Veg the leaves start to get a darker shade. I have tried to withhold any feeding and wait for them to get lighter but they never do. They never get light but rather darker and when I eventually feed them only the new growth/ top become a bit lighter. I have tried different feeding approaches(more/less) both with the young plants and also later in veg but the result is always the same - dark droopy leaves, clawing and generally a very stunted growth. I have top dressed with worm castings, made teas with just a temporary effect.

Recently I made an observation that the plants don’t develop a very good root system (yes, I could have checked this earlier) . In early veg roots are white, but not that thick or dense. After repot the new roots also appear white. The pictures show the plants in their week 8 of VEG, that is 4 weeks after repotting and the roots don’t seem to be strong or dense. You can also see that the plants are very small for 8 weeks growing.

Later in bloom the roots get brownish and plants start to get yellow with dying leaver starting from week 4 until the end. Plans don’t handle strong light and don’t drink as much. Harvests are poor and generally low quality.

I have posted pictures of a current batch in VEG and in BLOOM. You can see that the roots of both batches are not right. Is this root rot?
I am beginning to think that the problem is not caused by feeding schedule or environment but rather watering and lack of oxygen. I water every other day and generally have a good observation how much they drink every 48h. However, I might have overwatered on repot and didn’t water them for 5-6 days until they got light. Could that single overwatering start a root rot? Also, would you suggest to put pot elevators and additional perlite to the light mix?

Any suggestions and comments with regards to prevention and current actions are welcomed. I really need your help as this has been happening the last one year and I am running out of ideas and resources.


Environment: Sealed room, CO2 enriched (more info in the attached table)
Media: Plagron Lightmix (preloaded with mineral nutrients for 1-2 weeks at most)
Media pH: 5.8-6.4 (measured with a BlueLab multimedia probe.)
Nutes: Plagron Alga Grow/Bloom (100% organic, seaweed based) (find attached a veg feeding schedule)
Pots: ½ gallon (2L) for the first 3-4 weeks then repot into 2.5 gallon (10L)
VEG/BLOOM: 8 weeks veg and 9 weeks bloom
Lights room1: Chinese LED bar lights with Samsung LH281H chips (cold, warm and UV)
Lights room2: Quantum boards (fotops 800) with Samsung LM301B 3500/4000K
Light schedule VEG: 18/6
Water source: ph 7-8, 60 ppm, filtered through a chlorine filter
Seeds: Skunk XL from Royal Queen Seeds.

 

[Artful Codger]

Based solely on the appearance of your leaves (lots of texture and thickness, dark color, clawing), I'd guess you're both over-watered and over-fed. I'm not familiar with your specific brand of substrate, but watering every other day in a peat based media, in pots that big relative to the plants' size, might be too frequent. I'd try watering until 10% true run-off and not watering again until your pots are very light. That might be a better balance for how much water the peat is holding. If you prefer to water more frequently, a coco-based substrate might do better. For nutrients, I'd first try feeding by EC...not feeding until your run-off is 1.8 EC or less. Hope that helps.

 

[Three Berries]

I may water every 3 or 4 days on the big plants. I use 3.5 gallon pots. I've lowered my temps to the upper 70Fs vs mid 80Fs and they use a lot less water.

This current grow I'm planting directly in the 3.5 gal containers. But keeping the outside of the pot fairly dry and only watering the center until it gets bigger. I added a quart of perlite to the current mix, Ocean Forest,

 

[plan500]

Based solely on the appearance of your leaves (lots of texture and thickness, dark color, clawing), I'd guess you're both over-watered and over-fed. I'm not familiar with your specific brand of substrate, but watering every other day in a peat based media, in pots that big relative to the plants' size, might be too frequent. I'd try watering until 10% true run-off and not watering again until your pots are very light. That might be a better balance for how much water the peat is holding. If you prefer to water more frequently, a coco-based substrate might do better. For nutrients, I'd first try feeding by EC...not feeding until your run-off is 1.8 EC or less. Hope that helps.

I agree that watering every other day might be the biggest issue here. I currently water 0.4L every 48h. With that amount the pot does not get evenly moist and gets dry fairly quickly. I've been advised to increase it to about 0.6-7L and wait an additional day. In any case I lift the pots before I water so at this point I can rule out constant overwatering. Also I don't have a reason to water more frequently and coco not a path I am willing to take.

 

[plan500]

I may water every 3 or 4 days on the big plants. I use 3.5 gallon pots. I've lowered my temps to the upper 70Fs vs mid 80Fs and they use a lot less water.

This current grow I'm planting directly in the 3.5 gal containers. But keeping the outside of the pot fairly dry and only watering the center until it gets bigger. I added a quart of perlite to the current mix, Ocean Forest,

Will definitely add 10% additional perlite for the next batch but cant really change the pot size.

 

[snakedope]

You have mainly over watering symptoms
Like Artful has said, roots love oxygen, same as they love water, you need to make sure you balance the two, a healthy and vigorous root bowl will ensure a proper grow in all aspects, time, yield, quality etc.
It's best to water until you see run off then stop.
Wait until the pot is light or stick your finger deep and check moisture level deep within the pot before you water again
This will ensure that the water/oxygen balance is always at work
You cannot over water at once, the excess will always drain.
Over watering is time related, not qty related
Also, when you re pot always cut the root ball by at least 50% from all sides
This will boost your roots in the new pot and help it bounce back quicker if they were suffering before