Eh,not to be critical but that seems like quite a workload for a single cannister filter.I suspect that your filtration coupled with the water changes and some of those other fish you have are impeding your cat's growth.
Agree with Krich.
Its a 250gal, my filtration is a cannister filter which i clean and do 50% water change every 2 weeks, and tankmates include pbass, clownknife, paroon shark, bichir and a wolf
1. I must assume that your water is not ammonia-free. Perhaps not nitrite-free either. You must test your water by a liquid test tube test kit.
2. If you clean your canister every 2 weeks, you might be regularly destroying some (or even most?) of the BB's (beneficial bacteria) and get your tank uncycled.
3. The water change routine might not cope with the accumulation of metabolized chemical products in the water.
4. The tank mates are zealous and boisterous feeders and far outcompete the shy and timid catfish.
5. The tank mates you list can also be aggressive and simply harass and bite the catfish, which in turn prefer to not even come out when feed is presented and you have to throw it on their heads, as you mention, because they are afraid.
Both toxic water and aggressive tank mates = stress. Stressed fish have poor or no appetite and eventually wither away, get sick because the stress suppresses their immune system, and die.