Just a quick question.

[Kannubis]

How far from the top of the plants should my 400w hps be?

[Purple Daddy]

I suppose if you spent a few minutes searching this site or many others you could find an answer.

[pushit]

You should be fine 12-16in if your temps are good. Place your hand over the top of the plant for around 30 secs. If your hand gets hot raise the light. If the temp on your hand is comfortable you should be fine