did you transition slowly? My dog has really bad bellies I need to like take a month to transition it seems lol. I start really little with new food and then add more and more supplementing with the old until he is all switched. I agree though, BBwilderness wasn't the best for my pup, but I know some that do wonderful on it. Did you try adding a bit of pumpkin puree to his food? that can help with a fast transition as well. It keeps the poops nice, not too runny not too firm.
"There are two temptations to which people fall prey with dogs. The first is to think that biology counts for everything. The second is to think it counts for nothing"
- Tom Junod
“When you KNOW better you DO better.”
― Maya Angelou