I would keep vegging it for another month. Usually, you wait till it is a foot at the very least. Since you are height restricted, I am not sure really. You might have to get creative? To make it grow out sideways, you have to prune the center part..central node. That way instead of growing straight up, it is forced to grow up and to the left and right. You might also want to supercrop it to make a better yield. Google it as it is better explained on the net. These are all techniques for when you get a bigger growing area really.

As far as nutes go...if leaves turn brown, it's probably either a Magnesium deficiency or Nitrogen..usually mag. If they are a rusty colour then you're looking at calcium deficiency. Keeping the light as close to the lamp as possible without burning it will keep the plant short. Put your hand on top of the plant and if the light is too hot for you, chances are it's too hot for the plant.