Hi and welcome to YorkieTalk....Congratulations on your new babies!
You can use plain Dawn (the original one) dishwashing detergent to bathe them, it will kill fleas. Also, Frontline makes a spray that might be safe for young pups, IDK - you'll have to check the packaging instructions. If the spray is safe to use, I would bathe them in the Dawn and then use the spray.
The coughing could be kennel cough being that your pups most likely came from a puppymill. Is there not another vet you could take them to today?
__________________  ~Ruby, Reno, Razz, & Jack~ |