I just took my puppy out a few minutes ago and noticed a little red in his poop. It wasn't a lot and it was right on the end of where it started to come out. I just took him to the vet a few days ago with a stool sample because he was having diarrhea. The vet said he couldn't find anything in his poop and he looked good and healthy. I have been transitioning him from PurinaONE healthy puppy food to Blue Buffalo Turkey & Potato for food sensitivities because I think he was getting diarrhea from the food. I started him with 80/20 old food to new food, 60/40, 50/50, 20/80, and he hasn't had any diarrhea since I started with the new food so we gave him 100% today. I think there is a little red dye in the treats we give him, but I can't think of anything else it would be unless he ate something he wasn't supposed to. But he is acting completely normal, playing and all that. He doesn't whine when he poops or cry at all. He has a healthy appetite and drinks water regularly. Any ideas as to what it could be? Should I wait until he poops again so I can see if there is some more red in it and it wasn't just a coincidence?