If the Vet checked him out and said he is good health wise then buy some canned pumpkin (not pie filling) and add some to his kibble, it will help firm up his stool quickly. I would add pumpkin too each meal for a couple of days.
How late do you feed him at night? Is it right before bedtime? Maybe he has a late dinner and then has to poop afterwards?
Maybe the food you are feeding is too rich for his system, maybe you are feeding too much, maybe he gets treats that his tummy doesn't agree with, they can all cause runny poop.
Sinister "The Prince of Darkness" 4 yr old black male GSD 3.11.09
Draco "Dakota's Unbreakable Vow" 5.5 mth old male Dalmatian 6.30.13
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