I'd check your reservoir temps., firstly. Second, I'd try to tighten up your pH range. Thirdly, are the roots from the plants that are doing well, touching your nutrient solution / water? If the answer is yes, and if I'm reading your post correctly the plant's roots in question are not touching the nutrient solution / water, you have a potential answer to your problem. Remember too, that the only food these plants are getting is what you're putting in the water. If you're just using plain water, there's little to no food in there for them...you have to give them something. And just a caution, be careful with all that tinfoil, aluminum tape, whatever it is...this sort of material can cause hot spots.
I have 2 seedlings in a rdwc that are drooping and the lower leaves yellowing. I think I put nutes in too early but I’m not sure. I changed the res 2 days ago to just water but they haven’t perked up yet. I’m using GH trio at about 150 ppm and 5.5-6.0 ph. I have 2 other strains that are doing fine I think, but this strain I can’t seem to get right. The water level is about 2 inches below the pots and the few roots they have only reach about 1” below.
