Clown are a little thin and discoloration suggest early brooklynella, With Brook, mucus generally starts at the facial area as well as gills and spreads across the body producing lesions as it progresses often confused with ich and can turn into secondary bacteria. Other symptoms will be lethargic behavior, refusing to eat and heavy breathing from the mucus.
Apply ruby rally pro to the tank. The longer the fish are exposed to the treatment, the more effective it will be at eliminating this issue.
Temporary relief can be achieved by giving the fish a FW bath or dip in water same temperature as display tank. Even though this treatment will not cure the disease, it can help to remove some of the parasites, as well as reduce the amount of mucus in the gills to assist with respiration problems.
Are they breathing normal or labored?