My plants have been doing awesome for the first month. the other day i watered one with nutes. i have 2 rockwool stacked, and i only watered one because it was bone dry. i dipped the bottom 1/2 inch or so in the nutes for a few seconds and pulled it out. Should i be watering them differently? the next day, it was all droopy and straight up died. What could be the cause of this? now i have another one (pic below) same thing is seeming to happen. are they getting too dry before i water them? i can see that some of the skinny roots are brown, should they be white? my PH was around 5.5 and my nutes were pretty weak. PLEASE HELP! the other black will need watering soon and i dont wanna mess all my plants up?!

Attached Images

photo11.jpg (160.6 KB, 14 views)