My Babies Need Help

This is my first hydro grow got a little problem. I have 11 babies about three weeks old in 3.5in rockwool. I used 1/4 strength root 66 when I transplanted. The older leaves are uniformly turning yellow. Treated for overwatering underwatering and light adjustment. Could be nute burn but don't think so was wondering if this could be a sign of deficiency. Using straight water with ph about 5.7 do I need to start adding nutes?

Possible that they just weren't ready for the root66. I usually wait a bit longer before giving them anything but water. Cuttings do great with rooting products, but seedlings can grow a handful of nodes without food.

plants from seeds dont need anything other then plain water for first 2-3 weeks. BJ is prbly rite bout that root66 burnin em. also it mite of stunted ur plants if those are 3weeks old in the pix