Hello Sylvia,
When dogs eat their own or another dog's feces this is called copophagia and is actually somewhat common. A really great product for this problem is called Stop Eating Poop and is quite effective. I manage the blog here at Probioticsmart.com and would like to also point you in the direction of a blog post that explains more about this topic: Coprophagia: Why Dogs Eat Poop and How to Stop the Behavior. Good luck and let us know how things go for you.
Kind Regards, Emmy