I'm gonna agree with everyone else on the fecal. Just get it as fresh as you can. Check every day twice a day. When you find it, put it in a ziplock bag, and store it in the fridge til you can get it to the vet (asap!)

I also have to agree with Jeff on the meal size. The largest meal I give to any of my ball pythons is roughly 10% of their body weight. 2 adult mice should be ok, or a 25 - 30 gram rat.

I assume that you didn't mean that you just went from pinks to 2 adult mice. Were you feeding one adult mouse before? Even at that, the snake should be growing, unless there is something robbing the nutrients... parasites. I have a large girl that had a serious case of worms, ticks, and mites when I first got her. Once I got the parasite issue taken care of, she started thriving. I'm expecting eggs from her within the next month!

Steve