those ppms are too high. I suggest you change to plain h20 for a week. there is plenty of food in the cotyledons. every article I have ever read confirms that nuting before 2-3 weeks will lead to issues. nute burn is the end result after missing the warning signs of over fert, which include little to zero growth, distorted growth, excessive leaf curl, bright yellow viens, etc.
not saying they are overfert now but they sure will be in a few days.
do these plants have sufficient root length for getting into the DWC res? if so, than I would suggest to stop watering from the top. having wet rockwool in real DWC is problem causing. when you feel the root length is sufficient to life, than stop from the top
all my 2 cents