Chewy will replace your food if you think something is amiss, and Pro Plan will analyze a sample if you contact them, they want to know.
We don't get digestive upset here much either. But I would fast them 24 hours, to rest their bowels, then chicken or beef and rice for a few meals. As long as they are eating, drinking, peeing, pooping, playing and otherwise normal I wouldn't stress over it too much. If that changes, they need to be seen by the vet. Buy a new bag of food, and maybe a probiotic (I have been using Probios and love it) in the meantime.