Hi....
I've heard that keeping food in cans after they're opened is not a good thing -- you should spoon it out and put it in a tightly sealed tupperware. That might be what's giving your dog the runs. Also, canned food is mostly water so maybe you should cut down on canned and feed him more kibble.
My dog has a sensitive stomach -- so I only give him kibble and cook chicken & veggies for him. Sweet Potatoes are good too.
Purina One isn't that good of a food - it has alot of grain & glutens -- if you can, maybe consider changing to a grain-free food. I switched to Blue Buffalo. A very good food.
www.bluebuff.com 