It might not be getting enough light, but that's not the only problem.
Did you remove most of the leaves? Without leaves, the plant can't transpire, and it needs to do so to get nutrients from the roots to the upper part of the plant. That's probably why the plant isn't using much water.
One possible cause for the downward-curling sides of the leaves is closed stomata. Stomata are pores in the surface of leaves used for gas exchange. Most are in the underside of the leaves. They close when the air is hot and dry. So, I'm wondering what the temperature and humidity are inside your tent.