I am having this problem now, too.
My 1st gal did it when she was a pup, but she quit. Now we took in a year old gal and she frequently does eat poop. Now my original gal is doing it again, like she might be missing out on something. They won't eat pineapple and the commercial pills aren't for dogs this small, dose wise. I am at a loss as well. They are fed Orijen exclusively, and vet seems to think they are normal and healthy.