Hi and welcome!
There are many things that may contribute to what you're seeing. Tell us a little more about your pup so that maybe we can offer some helpful suggestions, things like how long you've had him, how long he's been on his current food, how often you bathe him or brush him. If you changed food when you got him, what was he eating before? Does he have any hives or bumps on his skin that make you think he's got an allergy or some sort of dermatitis? Could he be starting to go from a puppy coat to a more adult coat? Is he a full lab?
If you've had a vet take a look at him and the vet says it looks normal, remember this is your first puppy and the vet has probably seen hundreds or thousands of pups so I'd start out trusting the vet, who has actually seen your pup, over something you're read online at this early stage. His current food seems to have plenty of fats in it, which help contribute to a healthy coat. Grain-free foods are not needed by most dogs, incidentally. Any carbohydrates not provided by grains are provided by some other starch, potatoes, peas, rice, etc.
First puppy? Oh my! That's always an adventure! Come back and tell us more, and if you can get some photos on here, we love to see puppies!