It seems I've got everyone stumped lol. Anyone want to have a wild guess?
I have 2 guesses: #1 This could be as a result of stress or something from Ph swings over time, and is some sort of scar tissue, but doesn't affect the fish much/if at all
#2 This could be a result of stress or something from doing large waterchanges, with ammonia in my tap water and the prime hasn't locked it up quickly enough, so they are in fact being exposed to ammonia for a period of time. Not sure how quick prime actually acts.
Edit: My next move will be to contact the supplier and see if he is aware of anything like this.