Got a 7 week old puppy, spur of the moment, from someone in the market parking lot. The litter was being fed an adult sport mix dog food that, 1, seemed a little grown up for a babe, and, 2, wasn't available in our town. I picked up a bag of puppy food and have been feeding it for the last 3 days. Needless to say, baby has an "irritable bowel" and experiencing diarrhea. What can I do to ease the symptoms of this sudden change in food?