I have a poop eater on my hands!!!

Ok. Virga eats Doppler's poop. It's gross but it is what it is. I think we've narrowed it down to she's missing some Vitamin B. She'll only eat his. We thought at first that she was doing it to clean up the yard but we've gotten in the habit now of cleaning the yard up every day so we know it's not that. Maybe she's mimicking me? But I doubt that. She's also not in a confined area everyday and she gets plenty of exercise. She could probably use more and since the weather is getting nicer we're going to start taking them to the dog park tomorrow!!! Yay! But back to the poop eating. Neither of them have worms either. So she's not losing any nutrients from intestinal parasites. Like I said, I've pretty much narrowed it down to a Vitamin B deficiency based on my Googling 'poop eating'.

My question is, has anyone else experienced this gross habit and what did they do to help stop it? Also, did you change the food, add supplements, feed more, feed less? I'm at a loss right now. Any help would be appreciated.