Interesting, I'm far from an expert... But you moved them from soil to hydro? Mind explaining that a bit more? How big of a pot were they in? Did you unclump the dirt from the soil to get it into the new medium? Whats the PH of the reservoir water? The new growth, (Assuming it it indeed new growth) seems green and doing well enough...
Perhaps the shock to the roots from the medium transplant, or maybe your Ph or Temp is too high.
I know very little about hydro, But im sure more information would help you get a better response... For instance, whether their clones (Of course they are) how long ago they were transplanted, the lights their under, what they are being fed... Would all be extremelty helpful to getting a response....
Also, is it common for hydro setups to give plants so little room to form roots? Seems very small to me, but again, very unsure about hydro..