i know its too much but i have it 1 meter high from plant... what might be?? if some water fall on the leaves might burn it from the high voltage lampHi, the "yellowing" usually indicates over hydration, but not sure in your case. But that 400 watts of HID on a 13 day old plant sounds a bit much. At this stage, I'd be using maybe 125 watts of 5500K CFL.
Good luck & good grow.......BB