Light Burn?

[Bixit42]

So i swapped out my 250w HPS with my new HLG 260w QB XW 3000k, and one of my plants started drooping pretty hard the next morning.
HLG recommended a height of 18-24", so i put it at 27" above this specific plant at full light intensity.
I also had not watered this plant for the last 4 days because iv'e been seeing a few fungus gnats here and there.Wanted to kill off some of their larva population.
I gave her water at 6.6 ph yesterday just in case it was underwatering, and also dimmed lights to about 80%.
Coming home now, she has slightly perked up again, but i noticed the leaves on top seemed kind of yellowish.
This one is a photoperiod plant in veg, while my other 3 are autos currently in full bloom.
Only change i have seen in the 3 autos was all of them getting purple perioles over night after putting in the LED. The photo also got purple perioles AND stems.

Info:
Day: 42 Veg
Strains: Blueberry OG photo
Light Schedule: 18/6
Lights: 250w hps / 260w HLG QB
Light distance: 27"
Recent temps: 18-23c night, 22-27c day
Recent humidity: 50-72% night (yeh, got a dehumidifier coming), 40-60% day
Soil: Plagron Batmix 3/15/4 (pre-fertilized for 6 weeks)
Pot: 7-8L (She is probably rootbound as well, got a 20l airpot i will transplant into once the soil dries again)
PH: Soil is about 6.9-7ph. Watering with 6.5-6.7ph
Watering frequency: Every 3-4 days
Nutes: Nothing added other than a tiny amount of epsom salt and blackstrap molasses on day 37.


Is this just light burn?

 

[namvet25]

Doesn't look like light burn. Was the npk value listed on your soil bag?,if so what are they.

 

[Bixit42]

Doesn't look like light burn. Was the npk value listed on your soil bag?,if so what are they.

3/15/4

 

[Simplicio]

So i swapped out my 250w HPS with my new HLG 260w QB XW 3000k, and one of my plants started drooping pretty hard the next morning.
HLG recommended a height of 18-24", so i put it at 27" above this specific plant at full light intensity.
I also had not watered this plant for the last 4 days because iv'e been seeing a few fungus gnats here and there.Wanted to kill off some of their larva population.
I gave her water at 6.6 ph yesterday just in case it was underwatering, and also dimmed lights to about 80%.
Coming home now, she has slightly perked up again, but i noticed the leaves on top seemed kind of yellowish.
This one is a photoperiod plant in veg, while my other 3 are autos currently in full bloom.
Only change i have seen in the 3 autos was all of them getting purple perioles over night after putting in the LED. The photo also got purple perioles AND stems.

Info:
Day: 42 Veg
Strains: Blueberry OG photo
Light Schedule: 18/6
Lights: 250w hps / 260w HLG QB
Recent temps: 18-23c night, 22-27c day
Recent humidity: 50-72% night (yeh, got a dehumidifier coming), 40-60% day
Soil: Plagron Batmix 3/15/4 (pre-fertilized for 6 weeks)
Pot: 7-8L (She is probably rootbound as well, got a 20l airpot i will transplant into once the soil dries again)
PH: Soil is about 6.9-7ph. Watering with 6.5-6.7ph
Watering frequency: Every 3-4 days
Nutes: Nothing added other than a tiny amount of epsom salt and blackstrap molasses on day 37.
View attachment 937397 View attachment 937398 View attachment 937400 View attachment 937399

Is this just light burn?

I think it's light burn.
I had the same problem with two HLG 65 W Quantum Boards in hydro when I moved the lights 24 inches away from the plants.
I've moved the lights to 3 ft away, and that helped.

 

[Bixit42]

Here are pics of her from 2 days ago, if that helps.

 

[MickJ]

My guess is burn, if you are used to sitting under clouds and then you sit in full sun for a day, you would look similar. [emoji3]

Here are pics of her from 2 days ago, if that helps.
View attachment 937410 View attachment 937411

Sent from my comfy chair.
[emoji16][emoji41] [emoji43][emoji848]

 

[Bixit42]

I think it's light burn.
I had the same problem with two HLG 65 W Quantum Boards in hydro when I moved the lights 24 inches away from the plants.
I've moved the lights to 3 ft away, and that helped.

My guess is burn, if you are used to sitting under clouds and then you sit in full sun for a day, you would look similar. [emoji3]

Sent from my comfy chair.
[emoji16][emoji41] [emoji43][emoji848]

Yeh i'm hoping it's bleaching from the lights.. Guess i had a sort of similar case on a previous grow when i switched from 150w cfl to 250w hps.
Correct that plants in veg dont like as intense light as those in bloom? Could explain why my HBD which is about 17" from the lights has not gotten burnt yet.

 

[Waira]

-- Bix, I think that dry-out and the sudden light increase change did a 1-2 punch here,.... such a dry-out can cause sudden pH shifts, and if you're on the edge like you are at near 7.0 (should be about 6.4 give or take) it can start a lockout,.. roots hate that crap too, so find another way to deal with gnats, that hurts the plant more than them! Look into BTi mosquito granules/bits, a bacterium that gets ingested and kill the larvae... adults are little more than flying gonads, they don't really eat....
.... this looks mostly like the start of a micronute defc., in fact very likely since you haven't feed much (certainly the lights may have contributed to the paling as well); that soil is not a complete source for all the nutes, especially micro's,... the light stress can be a trigger for this as well,... and if your dry out drove the pH up, that makes even more sense as most of the micronute are metals, and lock out fast at that very pH range.
... get her well hydrated again, with nutes, and if you can get it, score a micronutrient supplement like Earth Juice Microblast; use in both soil and as a foliar spray...
...

 

[Bixit42]

-- Bix, I think that dry-out and the sudden light increase change did a 1-2 punch here,.... such a dry-out can cause sudden pH shifts, and if you're on the edge like you are at near 7.0 (should be about 6.4 give or take) it can start a lockout,.. roots hate that crap too, so find another way to deal with gnats, that hurts the plant more than them! Look into BTi mosquito granules/bits, a bacterium that gets ingested and kill the larvae... adults are little more than flying gonads, they don't really eat....
.... this looks mostly like the start of a micronute defc., in fact very likely since you haven't feed much (certainly the lights may have contributed to the paling as well); that soil is not a complete source for all the nutes, especially micro's,... the light stress can be a trigger for this as well,... and if your dry out drove the pH up, that makes even more sense as most of the micronute are metals, and lock out fast at that very pH range.
... get her well hydrated again, with nutes, and if you can get it, score a micronutrient supplement like Earth Juice Microblast; use in both soil and as a foliar spray...
...

Allright thanks for the reply!
Yeah i have ordered some beneficial nematodes to kill the larvae, but it's a 2-3 week delivery time
Will try to get some micronutrient supplement for them. Transplanted her into a 20l airpot with plagron lightmix as a temp fix... she was severly root bound. I'll try giving nutes to this one as the lightmix only has 1 week of nutes.

 

[sumhanf]

neem oil is killer for fungus gnats
i've had quite a population once
treated 5 plants with only 3ml on one liter water in a spray bottle
might have been very lucky there, but it did a good job
i can only recommend it to you plus your local flower shop should have it in stock
maybe you can use it until your nematodes arrive