nute burn or nute deff

Two weeks old seedling dwc. But itsonly a seedling so I just left them in rokwool but not in Da bucket just left it under my 150w hps but weird thing is I gave all my plants like 75ppms of nutes but all Da other plants greww except this one the leaves curled down and Da tips dry up and turned white and I flushed the plants with PhD Ro water just wanted to no if I shud just toss Da plant or stick with it