Complex Palm Tree Problem

Hey guys, I've had this palm tree indoors for the past 6 months now. When I first got it, the leaves were a gorgeous bright green and the tree trunk was mostly green. A week later, I had a serious fly infestation. Larvae was growing in the soil and after exhausting all possible solutions, I used a plant safe pesticide that stopped the problem. Then started a totally different problem.

The stems and leaves started drying up and turning brown. I had to cut them all off leaving the only green stem of the bunch. I'd water the plant only when the top 5-10cm of the soil was completely dry. I'd water it with about 50-100 ml of water.

When I first got it, the hole at the bottom of the pot was closed up. Humidity is at a minimal indoors and there is no natural sunshine that can reach the tree. Instead, I have an energy saving 50W spotlight aimed at it for 12 hours of the day. I've also attempted using a plant nutrient pellet (10 cm in length) to revitalise it but quickly took it out after reading that it could actually kill the tree.

It's been 5 months since cutting off the stems and the tree finally appears to be sprouting out new stems. Sadly though, the stems /leaves are turning white/brown and I'm at a loss to the reason why. If anyone has experience working with palm trees indoors, I would so appreciate your wisdom. Thanks a ton :)