I second taking Carter to the Vet just to check him over and make sure theres no medical problems going on.
How long have you left it before offering Carter something else to eat? Say he didnt eat his morning meal, would you leave him all day, then the next day etc, or would you offer him something else straight away/at the next meal time?
Dogs, Chi's in particular, are so smart. If they refused their meal of kibble just becuase they didnt feel like eating it, then they were offered something really yummy straight away, thats kind of telling them to keep on refusing
Its hard when they are so young too, as Chi's (particularly young ones) can get hypoglycemic - they need to have food to keep their energy levels up!
So, definately check theres no medical reason, hopefully someone else on here can help with the mushy stools - maybe a change of food is required, the Acana is too rich for him?
Is Carter free fed, or does he have set meal times?
I used to have this issue with my dog, Honey. She was such a pain to feed, so free feeding didnt work for me. We changed to meal times, and she did better, but still wasnt gobbling it up! We switched foods to fresh raw, and freeze dried raw, and now she is much better!
Also, if Carter is having too many treats throughout the day, he may not be hungry when meal times come around.