Help with plant issues in Hydro system

[ReddoggjZ]

Hello everyone,
I've already been through one harvest, and have been trying to do another harvest with two unsuccessful attempts. I put the seeds into growing cubes and after a week and a half to 2 weeks (the plants about 1ft tall with 4 small leaves on the top) then take it out of the cube and plant it into a drip harvest system. Twice I've had the same problem though where the plant, if I use the HPS light I have, starts to bend downwards and wilt. If I just use a small light, like a flourescent light, nothing happens though. The lights not very powerful though (only 150 watt bulb) so this is confusing me. I even put it like a foot away from the plant when it's supposed to be closer, and tried increasing the water that is going into the plant. I have moved into a new apartment so it's alright for now because there wasn't an easy way to transport the plant, but now that I'm in the new one would like to start growing again. Does anyone have any ideas... below I have listed my grow room:

small closet like 2 ft wide, and 7 ft high. I have a fan, drip system that's set to 5 hrs a day at periodic intervals, and 150 watt hps light.

THANKS FOR ADVANCE FOR ANY ADVICE!