Many puppies get those little ant bite looking bumps on their belly just from the nature of their former environment; in adulthood, its often associated with food allergies. Are you feeding a corn or wheat based food? It could be the cause of her issues. Although its very rare on the belly, wouldn't hurt to have the vet eyeball it and make sure its not a form of mange.
As far as the discharge goes, have the vet look at it; it could be a UTI. Those, too, are relatively easy to fix and common in puppies with inverted vulvas or crates with plastic surfaces that are not bleached and cleaned regularly.