My seedlings are dying help me!!

These lemon seedlings are struggling and I don't know why. They are roughly 2-2 1/2 weeks old and have been fed tap water ph'd to 5.8-6.1 under a blue cfl on 24 hours. The tips are going brown, with albrown spots aswell, and some have twisted. Can anybody identify what is wrong? The medium is rockwool btw

there hungry, get them some food.

Thanks for reply, will give them a small nute mix on there next feed