Thanks rachelanne.
All this made me think of another question: If the food is causing the problem, why is the diarrhea coming and going rather than hanging around all the time? It does clear up when I withhold food from her, but then she'll go several weeks with no problems while eating the Core. Does anybody have similar experiences that DID turn out to be food and not other health problems?
Is it kind of like the protein builds up and builds up in her system until her body just can't handle it, and then the diarrhea is a "natural" way of cleaning her back out?