Monty is 4 years old. I switched to Natures Variety Duck and Turkey several months ago and saw improvement with some skin issues, and he had much less gas. But his stools still are very soft. He just started a new bag of the food had has had very bad diarrhea for the past few days. He also just developed a couple spots on his back the size of dimes where the fur fell out. He used to get these frequently when he was eating Royal Canin. I feel like it has something to do with this bag of food. Should I try something completely different? If so, what? He seemed to do well with the first bag of the food (2 or 3 months worth), and now this. I don't want to torture him but I feel bad for him.