Fin Rot?
 

I have a purple tang, and I have noticed what looks like a bite out of his tail, and a couple on his top fin. Would this be fin rot? I have checked nitrate, nitrite, salinity, ammonia, and calcium, and all are within normal parameters. Is there anything else that could be causing this? He does have some tank-mates, a blenny and 2 small clowns

If it looks like a bite, it certainly could be a bite. That's a pretty common thing. If it is a bite, it should heal within a few days or a week. If it doesn't show signs of quick improvement, then it could be something worse.

A lot of times if its fin rot the damaged area will have a white edge.