My two senior basenjis have had food challenges since they were little. It's always been a struggle and they had pretty regular bouts of refusing to eat, itching and diarrhea from us switching the food or some food ingredients. We tried a lot of foods recommended on this forum, including home-cooked meals.
For many years we ended up settling on Acana Regionals Grasslands which is recommended by some here, is grain free and has mostly natural ingredients. It was the best food by far for our basenjis out of everything we tried. It is pretty high on protein so may not be the best for senior dogs.
Over the last year, we switched to Dr. Harvey's Canine Health Miracle Dog Food, Human Grade Dehydrated Base Mix for Dogs with Organic Whole Grains and Vegetables + ground turkey and coconut oil. It's been working great, they both enjoy it, are active, their weight is normal, and no more upset stomachs. I usually premake a batch for a week for both. 4.5 cups of Dr. Harveys dry mix + 2.6lbs of ground turkey (cooked, buy in bulk) + 3tbsps coconut oil (costco). Keep it in the refrigerator for a week.