Ok Discus experts, I need some help. I need to figure out what I'm doing wrong. I have had my Discus now for 3 months. There are 7 of them and they are in a 55g tank with 1 AC110 and 1 Ac70 for filtration. I do 2 larger 60% water changes a week with several smaller ones in between. They get fed 4-5 times daily with a variety of foods (NLS, hikari discus, frozen bloodworms, colorbits and omega one flake). 2 have grown quite well and are fairly big now. 3 have grown somewhat although not very much in my opinion and 2 (my blue diamonds) don't look to me like they've grown at all. What am I doing wrong and what can I do to get them to grow well? I have a thin layer of sand as a substrate (1/4" or less) one piece of driftwood, some watersprite and one sword plant in the tank with them. The Discus are active, responseive and colorful, they are not skittish and do not hide at all. This is my first attempt at these fish so I'm still learning.