Since it's HID you gotta be careful with the heat. So I'd suggest paying attention to that when considering the height of the lamp.
And most important to remember, especially since it's HID.. Your plants will likely stretch to about 2x their size, when you flip to flower, possibly 3x depending on genes. So you should take that into account as well since it would be a shame to burn the tops.
Also.. Your plants look a bit droopy.. It could be a lot of thiings, but most common is overwatering.. Keep an eye on that as well. And llooking at the lleaves, there could be some deficiency going on, but I'm not too experienced using fertilizers, so I can't say what it is.