This is hard to say. It's certainly good that she is eating and drinking and taking care of the puppies. I would be worried whether she may still have to give birth or whether she is breathing hard and grunting due to the presence of pain or a fever. It might be insightful taking her rectal temperature to make sure she's not running a fever. If her temp is over 103 ( normal is 100.5-102.5) or the heavy breathing continues, I would suggest getting her into a vet right away ( take the pups with you). Please note that although we are in lock down, bringing a dog to a vet in most places is considered a necessity, especially for emergency cases. Give your vet a call and ask whether they are open regularly. Wear a mask and gloves and practice social distancing if you need to go.