Recover from fungus gnat damage mid flower

Day 41 of flower
Medium: Purple cow Indicanja and Sohum
Lights: Mars TS1000, Mars TSL2000, HLG 165, Viparspectra V600 blurple to supplement
Temp: low 70's lights on, mid 60's lights off
RH: ~45-50 lights on, ~55-60 lights off
Grow "room": a section of my basement with panda film hung up as a light barrier. Not air tight and light proof enough to work. My basement is effectively a lung room.

I recently discovered that I have a fungus gnat problem. To be honest, I only recently learned how big of a problem fungus gnats actually are, so I didn't take the necessary preventative measures. The weird thing is, though, I ALWAYS wait to water until the top inch of soil is dry. I have 6 plants of varying strains, only one of which came from a seed shop. The other 5 were some freebies I got that appear to be some shit bred by Instagram people. Only one of my plants is exhibiting deficiencies that cause me major concern and it just keeps getting worse while the colas aren't fattening up like I want (obviously). I've already begun remediation for the gnats (had yellow traps out for a week or two, did my first mosquito dunk watering yesterday, going to get some DE this morning and switch to bottom watering for a while), so my question is: can I recover this late into flower? Seeing as how I've been using living soil and trying to be completely organic, could I try some synthetic bloom nutrients to feed the plant directly? The only liquid nutrients I've ever messed with is Neptunes harvest and compost teas. At this point, I don't give a shit if I kill all the microbes. I need to have a successful harvest.

Here are my other plants to show they do not have the same problems. All plants have been given the same treatment.

I have gnats luckily no damage like that, I have been advised mosquito dunks or diluted hydrogen peroxide

spliffendz said:

I have gnats luckily no damage like that, I have been advised mosquito dunks or diluted hydrogen peroxide

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Yea, forgot to mention that I just watered yesterday with some mosquito dunk water.

That should kill the larvae but your leaf issue could medium related, I notice the yellowing is appearing from the top and not bottom also speckling

Fungus gnats pose no threat to the plants.
It would take a severe infestation of larvae in the soil to cause a problem.
Yellow stickies for the adult flyers and 3 drenches with Gnatrol for the larvae.

The yellowing is pretty much all over the plant, not just limited to the top. It's not every single leaf, but most of them. I've run the gamut of deficiency pictures and once I found out how bad gnats are, I assumed they were the cause since one of the first signs of a bad infestation is micronutrient deficiencies. Seeing as how I've been using living soil and this strain has always been way taller and more lanky than the rest, it is absolutely possible that coupled with the gnats means the pot has run out of nutrients. I did another topdress of wormcastings and 4-8-4 a couple weeks ago so outside of feeding synthetic nutrients, I am not sure how much more actual food I can provide this far into flower. Not knowing what strain it actually is, I have no idea how much longer it needs but I am assuming 60 something days total. I could be wrong, though, because this is only my second grow so I don't know shit.

When I see dirty looking leaves I always assume the roots are in a worse state

MickFoster said:

It would take a severe infestation of larvae in the soil to cause a problem.

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What would you define as a severe infestation? The past two days I have found a larvae outside of the pots. One was dangling from the side and the other was drowning in the runoff. The first round of sticky traps I put out had a healthy smattering of them. Not covered, but if I had to guess, each one had maybe a dozen dead gnats over the course of a week.

spliffendz said:

When I see dirty looking leaves I always assume the roots are in a worse state

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What would cause that other than the gnat larvae because I have fabric pots so it shouldn't be rootbound. I keep them raised out of the trays so they don't sit in runoff. When I bottom water, I let them sit until everything is soaked up then raise them up again.

Hell, yesterday was the first day I watered since LAST Sunday just because I was being overly cautious about overwatering.

https://badpests.com/fungus-gnats/ has quite a few tips. The larvae are probably eating the roots. I guess not much you can do to correct it but keep trapping all around that pot. I've seen larvae happily alive and swimming in water, so don't water from the bottom or leave water there. put sticky trap all around that pot, above the top, around the drain holes, etc. you have to interrupt their life cycle which is only ~2 weeks. Since the roots are toast, idk. Idk mosquito dunks are they safe for buds? I'd try the h202 solution and water it with that every time you water. Maybe a little CaMg or epsom would help with deficiencies? My 2 cents.

raggyb said:

https://badpests.com/fungus-gnats/ has quite a few tips. The larvae are probably eating the roots. I guess not much you can do to correct it but keep trapping all around that pot. I've seen larvae happily alive and swimming in water, so don't water from the bottom or leave water there. put sticky trap all around that pot, above the top, around the drain holes, etc. you have to interrupt their life cycle which is only ~2 weeks. Since the roots are toast, idk. Idk mosquito dunks are they safe for buds? I'd try the h202 solution and water it with that every time you water. Maybe a little CaMg or epsom would help with deficiencies? My 2 cents.

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Ah, I didn't think to put a shit ton of traps out. I just put one on each pot.

I've got enough ideas swimming around in my head on controlling them going forward, I think. I am more worried that I am too late for this plant and it's going to die before it really matures. It's sticky, stinky and has decently fat colas that started falling over due to weight last week so it should be "good enough" but good enough doesn't cut it.

LawnXweeds said:

Ah, I didn't think to put a shit ton of traps out. I just put one on each pot.

I've got enough ideas swimming around in my head on controlling them going forward, I think. I am more worried that I am too late for this plant and it's going to die before it really matures. It's sticky, stinky and has decently fat colas that started falling over due to weight last week so it should be "good enough" but good enough doesn't cut it.

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I feel you. I don't know if it's fixable. I'm recommending concentrate on that 1 plant. There's probably more larvae there than anywhere else. Give that one more hypox soln waterings, etc. every little bit helps.