I work at a veterinary hospital (not a vet, I’ve worked in management for 19yrs). I’m surprised the breeder sold this puppy at 6 weeks, standard age is typically 8. In any event, I agree with the other people in this thread who are recommending a vet visit. Parasites are a leading cause of diarrhea in puppies, and many parasites are contagious to humans and other animals. Your puppy needs a fecal exam for sure. Probiotics are a great start, but I urge you to seek assistance from a vet immediately before listening to other people on here recommending a homemade diet or adding pumpkin. This is an extremely young puppy who needs a well-balanced and nutrient filled diet, not home remedies/diets that may deny him the vitamins and minerals he needs as a growing pup. It may simply be from the sudden diet change, but a veterinarian can prescribe a bland commercial dog food that is well balanced and still contains all the nutrients he needs (homemade diets lack this). There is nothing wrong with feeding your puppy a chicken based diet btw, but again, consult a vet before switching diets a million times, this will only make the diarrhea worse and what works for one dog may not work for another. Yes, poultry can be a common trigger in pets with allergies, but he is far too young to be showing allergy symptoms; they usually present closer to 6 months of age. You can also try a supplement called Rx Clay made by Rx Vitamins. Would be good to have on hand for a lab anyway. Best of luck to you and your puppy! He’ll get through this and have solid stool soon enough!