From personal experience a single 400 won't properly do that area, maybe half of it.

DP hit the nail on the head, 4 is a full house under 400w. Unless they're tiny, less than a foot tall.


I'd say vege your girls about 15-20" tall and squeeze 4 of em under the light, they'll overlap a bit but should be ok.


As for scent, keep your doors closed and sealed, If you can go out thru the roof, find a way to bring fresh air in from the floor, or floor level. Then make sure your exhaust fan keeps the room negatively pressurized so that any gaps or air leaks into the room are pulling outside air IN thusly preventing scents from escaping via unwanted channels.

This can create a heat issue, but enough cross flow or small AC or evaporative cooler on the intake should be able to take care of it. I had 2 400's in that size space and temps were manageable with an 8" exhaust fan plumbed out a window.