Upon closer inspection ( on my computer ) does the little black one have flakey skin? Skin flaking could be a sign of lice. Potbellies are BAD about contracting lice. Could also just be a white skinned black ( seeing as she has a white sister, the genetics are there. )
That's possible (probably definitely). I was just prepared to warn you that, glad you're aware! At least its easy to treat with a bath or two in prolate. Still not fun.