Nutribac: http://beanfarm.com/product_info.php...oducts_id=5933 - the directions state to add it to the water but since BP's don't drink often I just dust the feeder with a pinch of it. It's also good to keep some on hand to help a snake recover after an RI or regurgitation syndrome.
I would keep a log just on her for a while. Weigh her feeders, and try to get an empty weight on her every month. She may just be a slow grower.