One of my dogs will have loose stools if she eats more than normal. Although offered food twice a day, she typically eats late in the evening and wants at least two servings. When she goes over say 2.5 she will produce loose stools the following morning.
With a young dog, especially, I've noticed that washing the water bowl rather than just rinsing it, will help.
The bland diet (generally boiled white rice with chicken for flavor) should = more stable stools. That's what I've been told to use for digestive upsets for years. And it works.
What causes these? Maybe something "interesting" ingested, maybe more food than usual, maybe the water and possibly a "bug" -