I have them on paper towels, and clean the cage as soon as I notice anything (usually day of).

Also, just weighed her at 1095g. She has lost a whopping -26g since September (she gained weight lol, weighed 1069g on 9/12). I guess I'm less concerned, but its still frustrating. She has eaten 6 or 7 times since I weighed her then in mid September. Next time I feed her will be at night, but that's when I usually try anyways...