Not sure if this helps or not I had parrot cichlids that were turning black and I tried treating it with different medicines only to find out that some cichlids react faster then others to waste build up in the tank since I couldnt get a larger tank and didnt want to part with any of my fish I had to add my 55 gal tank now has 3 filters, 6 airstone bars and 1 bubble circle powered by 2 air pumps, 2 powerheads lots of air and filtration led to less build up of toxins in the water and the fish have all turned back to normal colors. test the water if that tests within ranges then try a vet. One sick fish can ruin a tank. good luck

That sounds pretty nasty, and this may be the wrong thing to say but Toeknee go to Aquarium Advice and look for the sick fish forum there. Now those people would be fishes if they could be and I would bet my elbow that they would be able to offer a good treatment.