Their color can also be influenced by the tank lighting. There's a LFS by me that uses lights that make most fish look amazing!
2 things I notice about your pic: the bottom fish looks to be a male, the 1 above it, female. Males are often more colorful & slender than females.
Also your water (or tank glass) appears to be cloudy green. Either can change the way fish look.
How long are you lights on each day? What type of bulbs do you use (LED or T-5?)? Color spectrum & wattage?