Just read though the most recent posts. I didn't realize you got another pup. I went through something similar in the fall. Pup had diarrhea (it was bloody, I have pics), wouldn't eat, went real weak on me. Turns out she was infested with hook and roundworms. It almost killed her it was so bad. I didn't take her to the vet, I knew it wasn't parvo from the smell. She got dewormer 2x a day at a higher dose and I syringed water into her until she was strong enough on her own.
Parvos usually shows in 5-7 days of exposure. So if you've had her longer than that and not been exposed from somewhere else (park, vet, or somewhere else unvaccinated dogs roam) then it's definitely something else.