I would try scenting with mice just to give it a shot. If they're starting to look worrisome skinny, then I'd be more concerned with putting weight on them than what exactly they'll be eating.

I also have had surprising success by skipping a week, waiting to see if the snake is poking just its head out of the hide, and then offering a rat that seems too big. I had an import male that hadn't eaten in over 10 months (so skinny a small rat would have been a big enough meal) start POUNDING good sized large rats. Once he started eating, he started eating everything, so I switched down to smaller, more appropriate sized meals, but that first one was definitely not what I expected. That same idea has worked for kickstarting snakes that were fasting during the breeding season, so it's worth a shot. A coworker suggested a while back, with the reasoning that maybe because the snake has gone a while without eating, it's waiting for something too good to be true to come by as a meal, rather than wasting energy on something smaller.

In any case, whatever the reason, that works for me sometimes. Worth a shot!

-Jen