I came across this link & thought those involved with this topic would find it illuminating. Although not addressing “senior” dog food, it gives good insight into dog food in general & rates the most popular brands. The formula for the rating is included as well as the ingredients & their purpose:
http://stormywinnscanecorso.com/id40.html
We feed “Taste of the Wild”, which is not on your list, but is well regarded. No grains in their food.
Thanks for posting that link. Since I have always fed my dogs Innova (on the advice given years ago by a shelter from whom I was adopting a dog), I was pleased to see their stuff rated A+. Not surprising, but nice to know.