I'm no expert on Neps but two things come to mind. First, are you sure you got the right kind of sphagnum? I unknowingly used some LFS that is meant just for lining hanging baskets and top dressing. It has not been good for my carnivores. I've switched to using LFS that's specifically labeled as a growth medium. Second, it sounds like the oldest parts of the plant are what you're worried about. It could just be natural for a spreading epiphyte to get old and worn out around its original rooting site. In nature, the parts of the vine farthest away from the "mother" plant would put down roots and establish themselves as separate individuals... Just speculating.

If that's the case, you might want to start new plants from cuttings taken from the vigorous parts of your Nep.

Regardless, I don't see how it would hurt to repot the plant if it's been in the same container for a long time. Sometimes old growing medium gets worn out and nasty after a few years, whether you're talking about plain potting soil or whatever.

Thanks very much. Those are some good ideas and information. The moss I am using is for orchid mixes and such.

Thanks again