Sick colt coral

[basssnake]

I have a hard coral which had a light brownish slime on it a week and a half ago. Most of it turned white, but 1/4 of the coral is still alive and I hope it recovers. The flesh seemed to have rotted away on it. Then about four days later my colt coral(or it may be a finger leather, i am not sure which it is, maybe someone can tell the difference) that started to look similiar and is starting to disenegrate slowly. The flesh of the stock is turning slimy and is sloughing off and the branches are slowly turning the same way and some have falling off. I don't know what to do. I checked the water parameters and there is no signs of ammonia(if there is, very very low) no nitrites, and around 20ppm of nitrates(which has stayed at that level for the last few months. So the water hasn't changed any. Should i remove it and throw it away?? Is there a medicine?? Should I leave it and see if it gets better?? It was doing fine before all this. I would upload pics here, but they are to big to upload. If anyone can help I would appreciate it, thanks, Jack