Thanks guys!
The tank is 8' long and 6' wide. The RTC's growth rate has slowed down by a lot, which is a good thing. At 28" he actually eats about the same as he was 18", 2-3 frozen markerels per meal. When small, he was all stomach.
The Dovii ate a lot of frozen fish in his first year. I switched his food to pellets in his 2nd year. He didn't eat as much as he did with the frozen fish and his growth slowed down since. At 15" in his 2nd year, I don't know if he will hit 20"+. However, he is still one of the longest cichlids despite bing the youngest.
The male festae is extremely heavy (3 lbs?), I think he will sure top 16". His first year was very frustrating, the female siblings outgrew him by 3 times, almost could eat him. Then out of the sudden he grew at the astonishing rate in his 2nd and 3rd years, and completely outgrew the female, now he weighs 3X of the female does.