Hello, I am weaning my litter of puppies they are all doing fine Except one
He will eat then sit in the corner and vomit he does not look good it almost seems he is alergic to the food. But he will nurse OK

On this question, I am out of my envelop on experience. One possibility I see is a restriction in his digestive tract that won't pass solids. On most medical items, a local vet is much better than even those on the net with more medical knowledge than I have.