How can we tell you how to cure something we don't know what it is, and how/why it happened? .......
be he is a dalmation coming into his spots.
be many open wounds, caused by virus' or pests or decor
be a number of things BUT
how can we know how to treat it if you don't give us information such as his behavior, his feeding habits as of late, how you are treating your water, how many times you clean it.
We can say "put him in 1 tsp AQ salt/gal for 10 days with 100% daily water change" but what if that is just going to harm him instead if he doesn't need it?
And what is to say that if we happen to get it "fixed" that it won't happen again if we can't see a bad habit pattern you have with something such as water changes?
You want to know what happened, well we aren't there looking at him, so we have to rely on you giving us information.
We can't help unless you help us.