I was wondering if giving some digestive enzymes might be helpful? My one dog is approaching 17 and her stools were becoming inconsistent, sometimes too loose and other times too hard. I read where older dogs sometimes do not produce enough enzymes. I started her on the following product to help her digest her food better and it is working amazingly well. I am not sure this applies to your situation but just thought it might help.
Digestive Enzymes and Probiotics for Dogs and Cats
Nancy
Digestive Enzymes and Probiotics for Dogs and Cats
Nancy