Hard to be sure by the pic but it looks like a nasty bacterial problem. Could be the result of injury from netting at the LFS. Don't think simple remedies are going to work if your seeing bloody red patchs around the "fungus like" area. Doesn't look like Lympho either.
How are your water parameters? NH3, NO2 & NO3? Are you seeing aggression from any tank mates?
If you don't have a QT tank, I would get one set up immediately, don't worry about cycling it. I would also suggest you begin a series of large water changes with well aged/aerated SW to reduce the DOC that will be fueling the bacterial problem if the QT is a few days off. Once the QT is up, corral the clown (without a net if possible) and transfer to the QT. You can use the water from the main tank in the QT startup to avoid a long acclimation time. Once there, treat with Maracyn II at double the dosage daily for 7 full days. If the Maracyn is unavailable, look for a SW antibiotic that treats gram negative bacteria specifically or post back with what is available if you're unsure.
You can also soak foods in the med (after predissolving in a glass) to speed things up. Just a few tablespoons would be needed and it can be done before each dose. Soak for about ½ an hour and feed sparingly. Be sure to siphon out any detritus from the fish and uneaten foods shortly after feeding to help maintain the water quality. You should also have enough SW made up at all times for water changes, the med will destroy the good bacteria as well and water quality will be an issue.
Cheers
Steve
