A nursing dog needs twice the amount of regular food, to help her produce milk and reserve energy for herself. Try giving her plenty of food and water to keep her producing milk and energy for herself, also she may have worms this causes waight loss and causes the dog to eat their own faeces, you might want to take her to a vet. If she does have worms you might want to avoid medcation, and if you really need to give your dog worming tablets you will have to hand feed the puppys with a dog milk solution as the medication could be harmfull to the young puppys.
Hope my advice helped.
Hope my advice helped.