oscar and convict cichilds

i currently have two convict cichilds both male (one smaller than the other) and one tiger striped oscar cichild. my bigger convict keeps attacking my oscar and smaller convict. i currently have three hideouts spread in the tank and the bigger convict has managed to control all of them he swims back and forth and whenever one of the others get close he bites and chases them away. and i am getting worried as i am noticing a lot of jagged fins and tails on both my oscar and smaller convict so a lot of nipping is going on. what should i do? should i remove the aggresive fish and return to the pet store?