Possible light burn? Or are the nutes too hot?

[Drago1980]

Intro: I'm running a Nirvana pre-99 Big Bud femenized 19 days into flower. She's in 100% coco inside a 1 gallon smart pot and is fed 3 times a day. Feed consists of 2.5 Grams Maxibloom and 1.5ML Calimagic per gallon of water, PH'ed to 5.5 (pee yellow). I understand the smart pot is on the small side, but past grows I've kept the plants very small - this one however stretched quite a bit and tripled in size.

Grow Details: She's been under a 300W (170W True) Old model Marshydro the whole grow. Room temperature is 70 Farenheit during the day, and 65F at night, AC controlled. The tent is a 2x2x4 with a 4" inline fan at 160CFM and filter. Light cycle is 2PM-2AM lights on. She gets water at lights on, halfway through the day, and a small amount just before lights off to keep the coco moist. I don't let it dry out. The distance from Light to canopy was rather tight the last week, but I've raised it so there's about a 8"-10" space now.

Issues: Today I went to give her the first water of the day and noticed brown/rust on a select few top leaves, right by the budding colas. It doesn't look like calcium def, since it's not tiny spots but more a smear. I'm also getting red stems on some fan leaves very recently. A tiny amount of leaves closer to the bottom of the plant are showing either moderate burn, or phosphorous def, with the tip very yellowed and curling up. Bottom growth is a bit on the dark green side, and top growth is a healthy lush green. The top growth for the most part shows only the very slightest of tip burn so I figured the nute strength was just about right, if just a bit too much.

My feed strength is low because the last few grows I tried using the KISS/Lucas method with maxibloom at 1TSP (6 or 7G) per gallon, and with my need to frequently water such a small pot, and the low intensity of light led to horrible nitrogen tox and and fatal amounts of burn. She hasn't given me any issues up until now and has been the best grow I've had to date.
In the imgur link, the pictures are showing the rust issue on the top leaves, red stems, and a shot of a lower leaf with the crispy yellow tip.

Any suggestions or advice? I'm inclined to believe I should increase the feed strength, as she's over three feet tall at this point but I do not want to make a bad thing worse.

If I missed any details you'd need answered don't hesitate to ask - I hope I provided enough information and hope I can get this fixed.

 

[LostTribe]

Intro: I'm running a Nirvana pre-99 Big Bud femenized 19 days into flower. She's in 100% coco inside a 1 gallon smart pot and is fed 3 times a day. Feed consists of 2.5 Grams Maxibloom and 1.5ML Calimagic per gallon of water, PH'ed to 5.5 (pee yellow). I understand the smart pot is on the small side, but past grows I've kept the plants very small - this one however stretched quite a bit and tripled in size.

Grow Details: She's been under a 300W (170W True) Old model Marshydro the whole grow. Room temperature is 70 Farenheit during the day, and 65F at night, AC controlled. The tent is a 2x2x4 with a 4" inline fan at 160CFM and filter. Light cycle is 2PM-2AM lights on. She gets water at lights on, halfway through the day, and a small amount just before lights off to keep the coco moist. I don't let it dry out. The distance from Light to canopy was rather tight the last week, but I've raised it so there's about a 8"-10" space now.

Issues: Today I went to give her the first water of the day and noticed brown/rust on a select few top leaves, right by the budding colas. It doesn't look like calcium def, since it's not tiny spots but more a smear. I'm also getting red stems on some fan leaves very recently. A tiny amount of leaves closer to the bottom of the plant are showing either moderate burn, or phosphorous def, with the tip very yellowed and curling up. Bottom growth is a bit on the dark green side, and top growth is a healthy lush green. The top growth for the most part shows only the very slightest of tip burn so I figured the nute strength was just about right, if just a bit too much.

My feed strength is low because the last few grows I tried using the KISS/Lucas method with maxibloom at 1TSP (6 or 7G) per gallon, and with my need to frequently water such a small pot, and the low intensity of light led to horrible nitrogen tox and and fatal amounts of burn. She hasn't given me any issues up until now and has been the best grow I've had to date.
In the imgur link, the pictures are showing the rust issue on the top leaves, red stems, and a shot of a lower leaf with the crispy yellow tip.

Any suggestions or advice? I'm inclined to believe I should increase the feed strength, as she's over three feet tall at this point but I do not want to make a bad thing worse.

If I missed any details you'd need answered don't hesitate to ask - I hope I provided enough information and hope I can get this fixed.

[URL=https://www.icmag.com/ic/picture.php?albumid=67772&pictureid=1610006&thumb=1]View Image[/URL] [URL=https://www.icmag.com/ic/picture.php?albumid=67772&pictureid=1610005&thumb=1]View Image[/URL] [URL=https://www.icmag.com/ic/picture.php?albumid=67772&pictureid=1610004&thumb=1]View Image[/URL]

Last pic looks sorta like a boron deficiency but could be related to magnesium with your low dosage of nutes I would say up the calmag to 1tsp per gallon and increase the maxi crop a bit also and see if that helps also need to check the ph of your soil mix.....

 

[Drago1980]

Thank you for the reply Lost! I've been doing some research and was also leaning towards either boron or manganese but questioned it since the PH of the nute+water mix is always between 5.5-5.8.

I wouldn't be able to accurately check the PH of the soil since I'm running pure coco coir ("soiless") and many threads here say chasing PH runoff in coir makes you chase problems that don't really exist. I would try a slurry runoff test for it, but being in a 1 gallon smart pot that is fully rooted, I'd be tearing away a substantial amount of roots as well.. plant would probably not like that too much.

I will increase the Maxibloom and Calmag as you suggested and cross my fingers - thank you again for your input! It helps tremendously to have someone else to bounce ideas off.

 

[Mikell]

Run off is a bad metric, even the saturated media extract method is regarded are too variable and inaccurate.

Slurry test with a soil sample is the most accurate and can be read with a digital meter.

But really, it does look like a pH issue, particularly a rapid swing. I get the same bronzing when I fark something up.

Common causes

-drying out (have you checked every pot before each watering?)
-overfeeding with soft water
-pH adjusting/testing too quickly (with a pen, obviously not a monitor) or excessively
-other stuff

The last one's a doozy.

Multiple deficiencies with signs of burn are more often a pH than pathogen, but that is also something to consider (too bad about that smart pot).

 

[Drago1980]

Mikell: Thank you for the confirmation that runoff/medium tests aren't the way to go. It's a single plant grow, and I do check the coir before watering - it's never dry and almost always pretty moist still.

You might have hit the nail on the head with the PH swings. I took a sample from my gallon jug earlier today which tested at 5.5 and let it sit exposed to the air for a few hours. It went from pee yellow to teal, so it's obviously rising at an accelerated rate.

My mixing regime is lukewarm tap water into the gallon jug, 1.5ML of Calimagic and shake, add the 2.5G maxibloom and shake vigorously, cap it off, and let it rest for a few hours. This results in a perfect 5.5PH level with no need for PH Up/Down. Perhaps using such a small amount of feed, it isn't buffering fully? I just whipped up a jug of 3.5G Maxibloom and am watching the test vial to see if it is rising as quick as the weaker batches were - I know Maxibloom buffers the PH pretty well so knowing my luck, my weak-yet-multiple feedings aren't ensuring a stable PH.

Thank you so much for your input! I'll do some more research and report back.