ok, so yesterday i foliage fed the plants and this morning i am starting to see that they are getting darker green veins on the leafs. I believe this is what i should be seeing, is this correct?

One other thing i just thought of, is it possible to stress a plant by putting it under a 600w MH light before it had a large root ball? Currently the plants are about 5 inches tall and they have been under the 600w MH light for about 2 weeks now, i'm wondering if i stressed them by putting there too early (if thats possible)