Hi there; I replied to you by email, but in case any one else is reading this thread and wants to know; none of the fish you have are fin nippers though you are a bit overstocked.
The main culprits for fin nipping are some of the barbs (Tigers are the worst), some tetras (mostly Silver tips, Serpae, Black Widows and Phantoms) and a few chiclids, mostly angels.
You can normally stop it happening by having larger groups (at least 6) of the fin nippers, as then they'll concentrate on chasing each other about, but to be on the safe side, none of those fish should be kept with guppies, Siamese Fighters or angels (I know you won't believe it after what you've been through, Tropical sunset, but angels can be nipped really badly by some of the barbs and tetras!)