yellowing /burning tips w.pic

hey guys
the tips on my 15 day old seedlings are yellowing and burning. they are in rainforest aeroponics No type of nutes have been added what so ever and i just need some advice on how to fix this. temp 75-80 light 400 mh hum. 35..
help please

Can't tell much from the pic. First thing that comes to mind is nute burn, but you havent added any. I would be asking myself if this was my plant...



Is my PH in range
Are my lights too close
Are my roots healthy
Is my airflow too little or too much, and is it blowing heat down from the light
What are my water temps
Is it hungry