I just got my puppy on Saturday. His poop was pretty solid until today. It has gradually gotten less hard and now is just runny. I have him on the same food the breeder had him on, blue buffalo puppy food. I want to switch him, but I wanted to get him settled and what not and was afraid he would end up getting diarrhea. Guess that didn't work out because he has it anyway :/. I am not sure if I should be concerned or if it is normal. Should I change his food?