if i were you i would put the light closer, 4 feet is too far away.
i would also transplant it to a larger container.
is the light a mh or hps?
mh put out less heat than a hps.
i would put the light like a foot and a half away from plant tops.
when light is set at the heighth you want, put your hand under it at the heighth of the tops, if your hand starts to feel like its burning, the light is too close, set the light this way and your plants should flourish.
i also suggest that you read up on these threads, you should be able to find the answers to most of your questions. the growers on here are very imformative and most will help if needed.
hope this helps
PEACE
AND
GRASS