Bulldogs World

My puppy is 12 weeks old. She had yellow snot and some gagging/coughing a week after arriving from the breeder. The vet gave her clavamox, which cleared up the snot, but did not touch the cough. The snot is now a thick, clear color and stringy, and the cough is still there but VERY productive. She really only coughs at night, but its a lot. She went back to the vet and they gave her clindamycin (spelling) which she has also finished. Still coughing and still has snot. Do I let it run its course as long as its not yellowish? She seems to feel fine. At what point do I take her to another vet or back to the vet?