I have a pond that is LOADED with CC.It had actually cleared some during the winter months. Now that the water has warmed, and the CC are active.......mud water. If I were a gambling man, I'd say that the biggest part of your problem are the CC. There's not much in there for those fish to eat with poor light penetration i.e. phyto-zoo-plankton. They are looking in the mud for dinner.

Give a man a fish, and he will eat for a day. Teach a man to fish and he will sit in a boat and drink beer.