Most chiclid diseases are due to bacteria, fungi, or parasites. There are many diseases the most common are fin rot, fish pox, slime disease,and ammonia poisoning.
My experience is with Angelfish. The thing I saw was simply something like depression. I had several that were simply rejected by the others. Then They quit eating and eventually were gone. I'm not sure what to do. They don't like to be alone but need to be with others they get along with. It may just be nature.
some of cichlid diseases are cichlid fin rot, cichlid swim bladder diseases, cichlid fish diseases, cichlid upside down, african cichlid diseases, cichlid white spot, cichlid freshwater fish, cichlid fish diseases.