[heidii]

Definitely take her to the vet. Weight loss is one of the only signs to tell if a prey animal is sick, as they hide weakness to prevent being picked off.

Also, is the hamster a dwarf or Syrian? 15g would be horrific for a dwarf, so I imagine a Syrian? I'd honestly also worry about the tubes with Syrians. Like Ria said, that's a lot more moisture, a much smaller space, a lot less ventilation.