I have been growing N. madagascariensis for about a year now with great
success. My growing environment ranges in temperature from about 58 F
to 82 F, and is illuminated by a 1000 W metal halide lamp. The plant is
about 5 to 6 feet from the lamp, and is illuminated for about 14 hours
per day. Watering is done every other day or so with purified water from
a reverse osmosis unit. Humidity is high, ranging from 75 to 95 percent.
I also feed my plant with small crickets which I purchase from a local
pet store. I believe that this is far better than using fertilizer.
Given the information you're provided, I would suggest providing greater
illumination and feeding your plant. Good luck.
Jeff Shafer