tips of leaves yellow 1 week old

3 seedlings 1" + about a week old. in rockwool,
not much roots showing
1x warm white
1x normal white
lights approx 2" from plants
last feed 5.5ph no nutes, but other 3 feeds wasnt ph tested

problem tips of leaves yellow got no pics at moment

any ideas?

got a fan on those things?

not yet but getting 1 tommorow