I don't use aero, but plants is plants, so here's what I see:

Your temps sound fine.

They look overwatered. I'm not sure how that is possible in aeroponics, but there it is. However, what you say about the leaves feeling brittle contradicts this. If the leaves are all feeling dry, then they aren't getting enough water. Quite a conundrum!

I have some questions:

  • It looks like maybe you had an overwatering problem, and that caused the wilt, but now the leaves are drying out in the wilted position. Is that accurate?
  • Are all of the leaves brittle, or just the lower ones? (The oldest pair of leaves do tend to die off at about that size.) The upper leaves appear kinda soggy and wilted in the photo, but it is hard to tell without touching them.
  • For how long have your plants been in trouble?
  • It doesn't look like an overnute problem, but did the problem begin shortly after you began adding nutes? (If it could be a nute problem, then it is a macronutrient problem, evidenced by the worst of it being in the oldest leaves.)
  • What is the pH?
  • What is the humidity in your grow area?
  • What was the ppm of your Brita water before adding nutes?
  • When you said you thought you had the problem fixed, but it only improved temporarily, what had you done that fixed it? Perhaps this is where the over/under watering comes in? Maybe they were overwatered and you cut back too much and now they are drying out?

    Since I don't do aero, I don't know what a good fix is. If my DWC plants looked like this, I would get a shallow container, put pH adjusted H2O and a tsp of H2O2 in it, and set each pot in that for about 6 hours, on top of the tub under the light, and see if they improved. But I'm sure there's a better aero solution... Hopefully some aero masters will chime in and have more experienced input for you.

    Hang in there - They aren't dead yet!