My little yorkie was also eating her poop ,I asked her vet and she sold me some packets called( for-bid ).you use a 1/4 of the pack twice a day mix it with their food for 5 days and it will stop them from doing this .I tried it and yes it does work . it is not harmful to the dog, and they will still eat their food ,but when it poops it tastes awful I paid about 2.50 a pack and it does 4 feedings.
Give it a try.