true parrot cichlids shouldnt be able to do much damage with their deformed mouth. They can't close it. This could be a jelly bean parrot with a more formed mouth. if the tank is under 55 gallons its a territory issue these things get huge when full sized and will easily need a large tank.
Did he change before or after you blocked the mirror? If he changed after it could be that he was used to thinking he was "seeing another betta" and it kept him from boredom.