I'd check with your vet also, if you haven't done so already. It may be the food, and changing food is a simple way to test the problem. If changing food doesn't help, definitely check with your vet.
A lot of members are looking at or have switched to versions of Purina Pro Plan. The dog food industry is changing not only in how they're marketing foods but in the nutritional science to formulate the foods.
If you haven't already, look thru this thread for some good information about how to choose your pup's food.
I would definitely check with the vet. I got Zekefur at 3 months old, and he was a really gassy puppy. He was having problems though. He was full of worms, had ghiardia and also had coccidia. He didn’t show any other signs except he was pretty quiet. Now I doubt your puppy has all that going on, but it could be as simple as needing another worming, even if it was done in the past month. It’s always good, and easy, to drop a stool sample at the vet’s.
I like to change my dogs' food every couple months so they don't get fixated on one kind. Of all the brands I tried, Blue Buffalo was one of the few that did not agree with any of them (or my cat for that matter). They all had various mild GI upsets, from gas to soft stool to really smelly stool, which resolved when I switched them to something else. So I am not a fan of the brand.
As for recommendations- there are sooo many dog foods out there. But I do like Fromm, Wellness, Royal Canin, Hills; as well as the ground premixed raw my butcher makes, for puppies. I have not had good outcomes with Purina, or with Orijen/Acana (my vet says those seem to be too rich for some dogs).
As someone else said though, worms can definitely cause gassiness as well. A broad spectrum dewormer as well as a fecal sample to the vet would be a good idea too.
You certainly should consult with your vet. I would ask about having a NutriScan analysis. It is a bit expensive, but if you have insurance they will usually pay for it since you will be using it as a diagnostic.
I don't think many vets are very knowledgeable about food other than prescription diets for various illnesses. Several years ago I went to dog food advisor and, as a result, changed to Wellness Core. The two little dogs did just fine, but the two big dogs had soft stools. So I recently changed to Purina Pro and things have improved dramatically.
Fun fact: Peggy's startled us with some LOUD toots! I giggle just typing this, remembering how she once scared herself. She was being a bit naughty, with her paws up on her pen, stretched vertically in all her spoo glory, trying to see out the window, when PFFFFTTTTTTTTTTTTTT! She got down so fast! It was more effective than any correction I could've given her ?
Hope you're having some luck exploring new food options for your little one!