Not enough light. Heat. A 400w HID is good for about a 2.5 x 2.5 area. 6.4 sq/ft.
1000w HID is good for a 4 x 4 area.
If you can swing it. When you get the money get a Mammoth 680w Mint White LED. Also has Dimmer Switch. Has a 435nm-730nm light spectrum, and uses the new EVO Samsung Mint White Diodes.
Will be available late March. The first run of them, and the 880w Mint White quickly sold out.
680w costs $800, and is 2006 umol.
At full power, and at 12in, it will cover a 5 x 5 area. Light distribution to the outer edges is very good.