We have two yellow african male cichilds that are chasing all of the other yellow cichlid fish. They killed one yesterday by nibbling on her fins. Now there is another yellow african cichild turning gray and another they're chasing that will soon be exhausted. All raised together. One of the bullying fish is in a temporary small plastic container in the tank. We tried putting all rocks once and all of our cichlids were acting weird and wouldn't eat even the purple ones. We have flower pots a boat logs and sand. What can we do?