Although I don't know hydrop, I'd say really REALLY reduce the nutes for now - too much at the moment and you are burning them. Poor things.

Usually I just use rooting powder and let them go for a few days before giving them just a drop or two of nutes then slowly up them, but I would be using soil in those cases and there are always some stray nutes in it generally, especially when fresh. Just a thought. Good luck! Hope they recover.