BP's grow a different rates. some are monster feeders and others are not. they're such fickle but lovable lil things. do u have her care records for feeding, weight, shed, poop, etc to help pinpoint any issues?
she's a gorgeous girl. chin rubs happen but will get better with each successive shed. the pooping is a concern but your tests seems hopeful. she's still new to you. maybe she just needs a good hearty meal. i'm sure u will feel better once u hit the trifecta - feeding, pooping (check x 4) and shedding but QT her regardless.
hopefully others will chime in on the pooping thing. keep us updated.