Why does my dog stink?

She cane back from the groomer people and still smelled. I give her a bath once a month and she still kinda smells right after I'm done with the bath. We visited the vet and we didn't mention this but the vet did say she had some extra feces in her butt because they use it to mark their territory. But my dog is spayed, so she doesn't have to mark too much. Could it have to do with this or something else?