icefins,
Is it actuall fungus looking ? Oscars and and many South American cichlids are prone to Hole In the Head. This sometimes starts off as fungus looking spots them turns into craters ( holes ).
If ick you will see noticable spots on fins, boby of the fish. Ich is very viss. at both early stages and late stages. So if it is ich you shouyld notice spots all over for the most part.
If it is Hole in the Head you will have to treat it because this is a disesase that CAN NOT be reversed but can be controled. With hole in the head the existing holes will remain and if left untreated can and will get bigger and deeper. But, don't let me worry you becasue not seeing it first hand I am just throwing out thoughts / speculations.
I kept oscars with my severum, leperinus species and my oscars had it. The other fish didn't though. Both oscars lived long happy lives but I am sure it was not a pelasent experience for them.
Hope this helps and Hope its NOT hole in the head.
Danny