[TS]

I found N. truncata needs very porous media to thrive, mine grew in perlite and sphagnum moss, placed under the tree receiving dappled sunlight. The pitchers are huge. I watered twice every day as this media mix can get dry quite fast.
Ali: if you obtained your plant not too long ago, then it could be acclimatising to your condition as what Alienfx said.
Jeff: I think your truncata need more water and sunlight, but make sure the water drains out every time you water. Water logged could cause root rot.