I'd start off getting a true ph meter and getting exact readings. You will need something better than drops for hydro.

Several thoughts....did you pre treat that hydroton? Do these plants have roots extending into the water? You said it was DWC; then said they were clones. They look extremely droopy which could either be from overnute, ph imbalance or perhaps they just aren't getting enough water. I don't have enough info about your system to say.
But I definitely see issues with your plants' health......unhappy ones.

good luck.