Mine were on Blue Buffalo for a while , but mine wouldn't eat the lifesource bits
so we switched.
The food never did anything strange to their bowels. They were softer for a bit during the trasnsition period , but that was only for a short while.
What kind of BB are you feeding? One of mine was on was on BB puppy and then I switched both of my dogs over to BB Wilderness. They had 2-3 solid poos a day.
Just make sure you switch
slowly . The poo may be softer while you transition , but my dogs were back to normal with in a week or so.