[Susan]

Hi,
The dry foods you mentioned have lentils in the first 4 ingredients, I’d avoid Lentils, peas would be a better choice like Cockermon said..

Yes cooking & introducing 1 ingredient might work to find out if your dog can eat & handle this ingredient & check out his poo & see is it firmer or sloppier, I did this when I thought Patch couldn’t eat potato, he reacted to ingredient in a LID vet diet Potato & Fish & the vet said it must be the potatoes, so for 1 & 1/2 yrs I thought he cant have potato & most g/f formula back 2014 had potato, so I started adding 1 spoon cooked potato & he was fine then I added 2 spoons of boiled potato & poos were firmer 🙂

Cheaper foods that might work??

Have a look at

“Whole Earth Farms”
Grain Free Recipe with Pork, Beef & Lamb (Poultry-Free)
For All Breeds & Life Stages
https://www.feedgoodness.com/products/recipe?title=Whole-Earth-Farms-Grain-Free-Recipe-with-Pork%2C-Beef-&-Lamb-(Poultry-Free)&id=8

Whole Earth farms – Grain Free Recipe with Chicken & Turkey
https://www.feedgoodness.com/products/recipe?title=Grain-Free-Recipe-with-Chicken-&-Turkey&id=1

Whole Earth Farms – Grain-Free Salmon & Whitefish Dry Dog but has MORE ingredients
https://www.feedgoodness.com/products/recipe?title=Grain-Free-Recipe-with-Salmon-&-Whitefish&id=7

Also look at “Victor Select” formula’s
there’s “Oceanfish Select Formula” or a “Lamb Meal & Rice Select formula” it has Probiotics & Prebiotics
https://victorpetfood.com/products

I’ve read alot of people who have dogs with sensitive stomach/bowel seem to do well on Victor dry food, just need to find the right formula & the Select formula’s have least ingredients to start with..

Pro Pac Ultimates
grains & grain free only has prebiotics