Yeah I'm not much on hydro but its not nute burn, it looks like its wilting more than anything, I would say it needed water if it wasn't in a hydro setup, r u using tap water, ph all that good stuff it could be heat. I know one problem with DWC systems is its easy to over water em, so I'd back off on ur water level or w/e u need to do to let it dry out a bit.