Why are my pitcher plant's leaves turning brown on the ends?

We bought a Nepenthes pitcher plant 3 months ago. It is growing beautifully but not producing any new pitchers (it has two small ones from when we bought it). The new leaves that come out and grow then turn brown on the ends. We live in Northwest Florida, and it is outside on a covered deck getting morning sun. We keep it wet with distilled or rain water and we have repotted it in a hanging coconut liner with sphagnum moss, clean sand and perlite. Any help to be given here? We are perplexed!