What date did he get his shot, some puppies have dif. reactions to vaccines. Try sprinkling a small amount of grated parmesan cheese on top of his food, the pungent smell usually will get their taste buds going.
If that doesn't work buy a package of boneless chicken cutlets trim off any fat, boil one cutlet until it is cooked, give him a tiny piece to taste, then shred a small amount over his food.
Babies have to eat, if he still doesn't eat his wet food feed him small amounts of the chicken just so he has food in this tummy, there is no nutrition in chicken so you don't want to keep him on just plain chicken for a long period of time.
If he hasn't eaten what you feel is a substantial amount of food by late this afternoon I would call your vet an hour before they close and tell your vet he is not eating. This baby has to eat.
I hate to see many changes of food in such a young puppy but you have to get him off that Blue Buffalo food and onto Royal Canin for puppies, do a longer transition, 10 days, each day add a small, tiny amount of Royal Canin to the Blue with the kibble, every day increase the Royal Canin amount, at day 10 he should be eating only Royal Canin.
Taking him out in the stroller is good, taking him to groomer before he has had all his vaccines is not good, your vet will / can trim his nails usually at no charge.
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