Fish are often described as having scaly burnt skin. This condition is generally due to the local water municipality doing a “chlorine pulse”. Since the chlorine has also hit the gills, the fish need to be treated by heavy aeration. Dropping the temperature also helps.
This condition is rare. At the chlorine concentrations that do this most fish simply die. This condition is also easily confused with slime coat syndrome. If one finds a fish like this one should also treat for slime coat syndrome. Here is a link to that syndrome:
Aquarium Science Website
The chapters shown below or on the right side in maroon lead to close to 400 articles on all aspects of keeping a freshwater aquarium. These articles have NO links to profit making sites and are thus unbiased in their recommendations, unlike all the for-profit sites you will find with Google. Bookmark and browse!