Firstly, I found that whenever I fed my previous dog with anything that contained chicken, he would have vomitting or diarrhoea. It could be that your dog is allergic to chicken or, that he wasn't gradually introduced to it and it was too rich for him.

As for copography (eating other stools) it is common with dogs. They never eat their own but will eat others. To us it is disgusting, but to them, it's like eating chocolate - that's how the vet described it to me. You can get pills from the vet which will help to cut the habit out.

I found this info below which may help you.

EATING STOOL (COPOGRAPHY)

Distasteful as it seems to most humans, eating stool is normal for dogs. (New mothers, for example, will eat the stool of puppies, presumably to keep the nest clean. Puppies, in turn, will sample whatever they come across including stool. Human babies explore with their hands, and puppies explore with their mouths.

Nearly every dog will occasionally sample stool but some have a real craving for it, including their own, and will eat it every chance they get. This may be caused by nutritional deficiencies possibly due to a lack of certain enzymes in the digestive tract. When a dog eats his own stool he is giving the partially digested food another run through his digestive tract where more nutrients will be absorbed.

In some cases, dogs will eat stool merely because they don't have enough to do or they will do it because it is a way of getting your attention. They will also eat stool as a way of establishing their dominance over other pets by removing their scent markers. (dogs that are wrangling for dominance will sometimes pick fights as well.)

NOTE - Many of the problems listed above can also be caused by a serious condition called obsessive-compulsive disorder. Like people who are obsessive about washing their hands, for example, dogs may be obsessive about biting at their skin, over eating, finicky eating and the like.