Is it possible that they all have some sort of parasite? This happened with Sophia and her diarrhea would not go away for months. We tried multiple rounds of antibiotics (which always helped the diarrhea when she was on them), blood testing, 3 stool tests for worms, tried changing her food in case it was an allergy. We were about to schedule her for a biopsy of the intestines, when the other vet suggested trying panacur, it's cheap and we don't really have anything to lose. Sure enough, that fixed everything. So the vets best guess is that she had whipworms. This was over a year ago and no more long bouts of diarrhea since
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