Exactly. Usually dogs will eat most anything so if they stop eating a food that they normally liked its a sign that something is wrong with the food or something is wrong with them and they should be looked at by a vet.
I have a Lab and the biggest red flag is when she doesn't eat. When she's healthy she's like a garbage disposal with 4 legs and fur!
LQ
Mine will eat ANYthing remotely resembling food. She's pretty good about not eating non-food items, although she does chew the tags and any other protruding small appendages off her soft toys. Fortunately she doesn't swallow the bits, she leaves them lying around . . . she just chewed the eyeballs off her stuffed lizard, I found two little mournful eyes staring up at me from the living room floor. I sewed up the holes and made the little reptile black "X"s for his eyes.