Red stuff on tail

[Greener]

I have a white betta and I just got home from vacation all my fish are still alive and the only problem seems to be with my white betta, he has red around the end of his tail, it looks like pellets that have not disolved. Is this some kind of parasite? or is he biting his tail?

 

[BrookeLea]

is it hanging off? does it look cottony or is it flowy? it's hard to tell really...can you post a pic?