Right now they are just on paper towels with small hides (that they use). There are some plastic bits on the lid that could be causing such a mark if they were pushing on them enough.

I have some ReptiChip, so my current plan is to put them in bigger (sweater box) size tubs and give them a burrowing substrate along with some moss.

I also wonder if I should feed them more. Both are around a year old, though the girl pictured is considerably smaller than my little guy I raised, so maybe she is trying to make up lost weight. Currently feeding them rat pups on a 10 day schedule.