Looks like a nice peaceful setup. I find parrots and firemouths change to suit their tankmates. Put them with peaceful fish and they will be peaceful. But put the with something they have to vie for dominance with and they will stand up for themselves. Obviously there's always the exception to the rule. Some cichlids are just jerks. One of the most aggressive jerky cichlids I've owned was an old beat up bolivian ram. It would stand up to JDs, parrots and even a young male GT. It would actually go out of its way to pick fights with them.