How far away do I start a new 400 mh light from tops of these babies
A good distance for a 400W is about 20" away to start. If the seedlings are responding well you can move it a few inches closer at a time, and after they're growing fast, you can keep it about a foot away (as long as the temperature feels okay if you put your hand where your plants are).
I noticed they're a little droopy. Just curious, are you using anything to help control root rot, like Hydroguard? I saw the temperature is staying between 70-84°F, which is good