My GSD mix is 16 months, and the last 2 days first thing in the morning she has pooped on the rug by the door that she goes out for potty. She hasn't had accidents in a very long time. Nothing has changed in the household or food wise. She hasn't been listening as good as she used to so I have been doing more training more often. Could it just be behavioral? Or do you think a vet visit is in order? She just had all her shots and annual 1 month or so ago and the vet didn't find anything wrong.