Circle or crescent spots on Foxface
 

More like half moon top & bottom. Consitant size & shape about the size of an eraser on a pencil. When fish is dark the spots show light, when fish is light the spots show dark! Spots only on the right side of the Foxface...none on the left??????? Looks like bite or suction?? marks. No predator fish in the tank. Largest fish is just his buddy a Sailfin. Any ideas?

I actually saw a spot similar to what you described on my foxface too, but it went away after a few days. Had no idea what it was either..

Foxface fish have incredible camoflauge coloration, they will display that when stressed, or at sleepy time. Was that possibly it?

foxface
 

Just an addon to what Deb said, my foxface can be bright yellow to a mottled grey with spots....very fast..depending on mood ,stress....
"Oscar" is also a pig, and is constantly scuffing himself hiding and playing with the Tang (Felix LoL)...I used to worry but he heals very well...even a good scuff (black or white spot etc) will heal in 2-3 days.
Personally , I think removing fish to treat anything drastically reduces there immune response ( macrophage cellular) for days....so the choice is to treat/medicate with a comprimised immune system or let him heal and add a little garlic to steady your nerves.
my 2 cents ....GOOOOOd Reeeeefing!!!!!!!