Well your water parameters were a big problem when you last posted.. the ammonia shouldn't get but half that ever. Your tank isn't cycled and you can't cycle with a cichlid.. you shouldn't keep one with a betta either. They'll eat him.. You need to rehome the cichlid or get a school in their own tank.
As for the cycling, you should be testing daily and doing a 50% change any time you see either ammonia or nitrites. Cycling will take up to two months (from the time you introduce fish not set the tank up) and after it is cycling you will have no ammonia and no nitrites and some nitrates. At this point a weekly 25-50% with siphon will be enough.
Ends are black, I see fin rot. It probably started with the high ammonia and nitrites, plus lots of stress from the stocking.