Our 8 week old border collie puppy had severe diahrrera. We took him to the vet, she gave Trimethroprim Suofa 480 mg. for one week, one dose left. The dog has a more solid poop but it has a layer of white mollusk looking stuff around it. And sometimes even though the first poop is semi solid, the second poop is liquid and hard to come out. The pup has begun scooting his butt across the yard after pooping. He has had one 5-way shot when he was 6weeks. ??
Your pet may have intestinal parasites and I recommend that you go back to the vet and don't forget to bring a stool sample. Vetcare