This sounds more like an allergy or some sort of parasite than "wet tail" to me. The major symptom of "wet tail" would be diarrhea/loose stools as a result of an intestinal bacterial infection. I do not have much experience with piggies so I hope someone else can chime in.

Are there any other symptoms? How long has this been going on?

It sounds to me like this piggie should be taken to the vet! Kalena should also be separated from any other piggies!