Hi, wonder if anyone can help; my puppy is 9 1/2 weeks old, we have been fading out his old food that the breeder gave to us and have put him on Hills 'Natures Best' for puppies - he has been fine on this but in the last three days hes been sick twice and stools are runnier than normal..could this be the food?? other than this he has been quite well in himself, but today hasn't eaten at all?? Any ideas?? Thanks