personally, if i was you, i would get rid of everything in the tank(rd are very mean, and can easily kill the other fish off), and do a few cool cryptoheros family fish. They are pretty cool and stay small. Stay away from convicts tho, to mean(but i believe the were moved to something else, but i don't know, i can't keep track of all these changes). But you atleast need to get rid of the rd, they can be very mean, look in my avater, he is only 5.5" and has been like that since i got him at 3".
male jd can get up to 12" but normally max out at 10", females are smaller. Convict males can get 7"( but will beat the snot out of everything once in breeding mode) females around 4'. Red devil max out at around 12"-14".
Tank is way over stocked, and is a waiting blood bath.