Should I Be Concerned?

Well, I already am concerned, but should I be even more concerned with this? Last night I noticed that there were a few half-eaten food pellets next to my chins' two food bowls. This normally never happens. There were also a few crumbs in the bowl, which isn't too unusual so that didn't worry me too much. Other than that they ate all of their food. My first thought went right to teeth issues, so I immediately gave them both sticks. They chewed on them happily, no change in chewing patterns...

Should I Be Concerned?