Dog food

I think some of it is the aging process, every dog I've ever owned seemed to get more gassy as they aged.  Not much different than people.  It wouldn't hurt to try something else but mix it with what she's currently eating as you transition.  My vet  said to stay away from the boutique brands that litter the pet store shelves now.    He recommends Purina Pro Plan, Science Hill, and Eukanuba.  My 2 english setters that hunt a ton do great on Purina Pro Plan Performance 80/20 Chicken and Rice Formula.  ​

We just started our 6 yr old GSP on The Farmers Dog 2 months ago. He cannot get enough of it. Eating far better than he did previously 

American Natural Premium, been feeding it for years with no issues and they've never had a recall.

I use this for house dogs:
https://americannaturalpremium.com/product/original-recipe/

I use this for my hunting dogs:
https://americannaturalpremium.com/product/endurance-plus/

The Endurance Plus is high powered food, I raise and train beagles and they are run nearly every day.
If your not working you dogs often, I would suggest the original recipe.

Both are all life stage foods as well, no need for puppy food nor senior food.

Note, corn is a cheap filler and has virtually no nutritional value for a dog.

My vet warns against grain free , it can lead to heart problems in dogs.

Try the grain free lines.

I cook my dogs food. 2 labs. Ground turkey, peas, carrots, sweet potatoes, eggs. I add ground flax seed and bone meal. Try it out. Your dog will thank.