3 year old dog repeated diarrhea

My three year old Berger Picard Timber keeps getting diarrhea. We’ve done stool samples and blood work and my vet said everything looks good. She was prescribed antibiotics (Metronidazole 250mg) and nutramax proviable forte digestive health supplement and Royal canin gastrointestinal canned food. She was ok for over a week after returning to her regular diet of Blue Buffalo life protection formula lamb and brown rice (she has always been sensitive to chicken and eggs so we spend a little more for the lamb formula) , then the diarrhea started again all over my house. She is unable to make it to the back door but she tries to. I’ve also noticed she hasn’t wanted to play with her toys for several months and sometimes her tongue and gums look pale to me however our vet said they didn’t look bad. I also have two other dogs that are fine. I don’t think she is getting into anything because she doesn’t go outside without me for more than five minutes. Any advice would be greatly appreciated. I love my Timber and I hate to see her ill.  Thank you

Hello - diarrhoea can happen secondarily to other conditions, perhaps including liver disease or pancreatitis, Addisons disease, EPI and various autoimmune diseases.  I wonder whether more tests might be on the cards.  Good questions for your vets include, 'What possible causes haven't been ruled out yet?'   Then, 'Could any of these be urgent?' and 'Which would be the most common?' and 'Which are easiest to rule out?' because the answers to those questions will often  determine which tests your vet chooses to do first.  Stress is often a tricky one and may be worth a discussion.

One differential that I didn't list there, because your dog is only three, may be cancer, which sounds extreme but should also be on the list.