I have had my Discus now for about 3 months. I know some of them are stunted and apparently it happened before I got them. I have 2 that have grown a lot, 1 that has grown somewhat, and 4 that don't really seem to have grown at all. This could be just me because I see them every day. But the 2 biggest are a fair bit bigger than the smaller ones. I've been feeding as often as I can, usually 4-5 times daily. They are getting NLS pellets, omega flake, bloodworms, Hikari discus and tetra colorbits. Not all of them will eat everything, but they are all eating. I change 50% twice weekly and usually a few smaller vacuums in between. I have an AC110 and an AC70 for filtration and they get cleaned regularly. What am I doing wrong?