i have a firemouth that will not grow and looks a bit off in color.it eats fine but is not keeping up with the other two i have that are growing and are developing colors that give a german ram a run for the money.i feed frozen foods like blood worms,brine shrimp,plankton and a cichlid growth formula.flake is omega one veggi and chichlid formula.they are housed in a 90 gallon with three green severum as tank mates,all get along fine.my p.h. is 6.5 hardness about 15 temp is 78.so i'm lost in need of advice to what may be a problem.i have never kept south or middle american cichlids i have kept double trunk elephant nose fish for the last seven years when my last one passed,heart broken i decided to go a south cichlid.so i could go for some expert advice.thank you in advance.