[Unclenugs]

hmm... looks a little yellow... the RO water you're using should be at an adequate pH, but the yellow makes me lean toward a pH issue, or overwatering. sometimes rockwool holds too much water for little seedlings. I'm hoping someone with a little more experience with seedlings can help out here, as I have more exp. with clones than seedlings...

sorry I can't be more help man. Best of luck.