looks like a basic aggression injury to me i see similar ones very frequently caused by scraping agains taracotta pots, rocks, or being swiped at by a fish with a large mouth like a pike cichlid. the fact that hes had so many problems leads me to believe there is possibly something wrong with your water chemistry unless you were just really really bad about quarantining allot of fish. do you have a high ph or poor water quality? a combination of unprestine water with unfavorable ph can cause issues big issues for cichlids. if youre keeping the ph purposefully really low you could have problems with ammonia nitrite and nitrate because theyre harder to control in a low ph warm environment. things as simple as electrolytes and carbonate could help prevent allot of disease in aquarium fish.