Light stress? Nutrient burn?

I see you using pod poppers for your Gnats. I rip open the bags and sprinkle the little sacks everywhere and even mix them into the soil a bit. they have always worked really well for me. bt pucks are also an option. can get them on amazon as misquote pucks or something like that. your ph looks on point for soil grow just wondering how stable it is. I have to aerate my water to stabilize the ph in it. example: if i just ph it once with no aeration, I need 3-4 drops of acid per 4L of water then I use it. When I aerate it I need 10 drops to get to the same range after 2 hrs of bubbling. You could also try letting it sit out for longer time to allow it to settle as well. I use phosphoric acid at 85% as my down. Citric acid based downers are not as effective. I also use Gaia green and find they need a bit more magnesium to keep things in check and that its a bit heavy on the N, May want to try mixing it in a ratio of 50/50 or 70/30 of grow/bloom for vegging. It also have enouth Ca in it so if thats showing issues for calcium its PH. The seaweed extract should be adequate for potassium and avoid any problems. Good on you for fixing the lights this should help them a bit. I noticed in my grow I got my one plant can take way more light then the other one, the one that's more sensitive burned up much like yours. With your clover cover crop also growing it it will be using up nutrients as well and only will release the atmosphere nitrogen back into the soil when its decomposing. Good Luck!