Could be a few things... What are his temps like? Sometimes too hot/too cold can throw them off their feeding schedule. Does he have lots of things to hide/burrow in? Baby corns will sometimes go off feed if feeling insecure or uncomfortable in their environment.
How long is 'awhile'? One of my babies is a little finicky, sometimes he'll refuse to eat for a month or so before picking back up again like nothing ever happened!
Have you changed mouse suppliers? I've heard of snakes being turned off food from different suppliers, they smell different.
Tried any feeding tricks? Overnight in a deli cup, covered up, brained/slit pink, really hot pink?