it can't be a mag def. cause you're not feeding those seedlings yet are you??? all i can really see are some of the edges of the leaves turning up. usually means too much heat.
that's kind of what i was thinking, the light was around 12+ inches from plant, now it's 24in away. will the leaves go back to normal so i can tell if that is the problem? so far nothing looks diferent.
Leaves curl up like that when there is low humidity. The heat from your 400w MH will have lowered it. In veg, keep the humidity up. In flower, keep it as low as you can have it.
unless leaves get crunchy, they'll be/go back to normal soon. i doubt if that's caused by low humidity. in veg, i like to keep it around 40-60%. in flower 30-40 is good, for me. you can get 400 watts pretty close to your plants w/o heat issues. especially if you have an air cooled hood.
Upcurling leaf edges are a sign of low humidity. The leaves curling are the plants way of reducing surface area from which water can evapourate.
the humidity of my room is around 18-30% the whole time; and my leaves never curl up---- gotta love living in the desert
this statement don't hold water, since the lions share of the stomata are under the leaves. do a search.