I hope you had him in quarantine before you spotted the mites. Never a good idea to bring any new reptile into your clean collection without quarantine of a minimum of 3 months...parasites are just one reason. The getting the mites and treating are two reasons why he might not be eating. I'd wait until he's fully been treated (use something like Provent a mite to really do it first treatment) and then offer food again. Every week or two is fine and make sure you try late evening/night and with a very hot mouse. Dippng the nose in boiling water just before feeding can sometimes trigger a good feeding response in reluctant animals. When was the last time he shed? If he's approaching shed, he might not eat either. Do you have feeding records on this animal so that you know if he's done this before? Balls go off food constantly...part of the reasons why I dislike them so much. I wouldn't panic though...they can go a long, long time without food. At this point though, I would definitely quarantine for at least 6 months. Balls and other pythons can carry IBD and mites are a suspected carrier. While corns can't die from it, there's no telling if they can be carriers without being affected. It would be a real tragedy if you brought a lethal disease into a clean collection because you didn't follow quarantine protocols. I know of several people who are currently paying the price of not putting animals into quarantine immediately.