Your vet will know your dog's situation best, but I will share an experience I had with my younger boy who has had occasional diarrhea for unknown reasons:
Sometimes the dog's digestive system needs a rest after an episode of diarrhea. I have withheld food for 12 to almost 48 hours, only because I am confident Teddy doesn't have any other health issues, and he was always supervised. I have never withheld water except before anesthesia as instructed. Please be very careful to ensure that your dog is not dehydrated.
Overfeeding in general can cause problems, or feeding the wrong thing. I am really strict with Teddy's diet. Usually steamed, plain chicken breast and white rice will fix his problems. Then I put him back on his kibble. One time the chicken didn't work and I put him back on his kibble and he went back to normal.
Also, my Teddy was given prednisone once and he didn't do well with it so the vet had me discontinue it -- but discuss with your vet first.
Did your vet prescribe the probiotic?
Any lethargy or other symptoms? Definitely get back to the vet if there are any other symptoms.