I think you are currently overstocked. Do you test your nitrates ? That will let you know if you are overstocked. I usually change 50% of my water when nitrates hit 20 ppm some change at 40 ppm. How often your tank needs a waterchange tells you if you are overstocked. I don't want to change my tank more than once a week so I keep my tank lightly stocked (75 gallon with a 5" chocolate cichlid, 3" spotted raphael, and a 2" texas x bp hybrid) the hybrid will be rehomed as the fish get older.
Convict and firemouth can crossbreed also and if that happens they will try to claim the tank! I have been told kissing gouramis can take over a tank if they get picked on by cichlids pinning them into the corners of the tank.
This is just my opinion my .02!