[anonymously]

What does your vet say? It is not about what is the best food at this stage of his life. It is about what agrees with him. I am thinking that some of the high quality foods may be a little too rich (fatty, greasy, high protein) for him.

Maybe a bland, boiled chicken and rice diet would be better. Consider consulting a veterinary internal medicine specialist, otherwise, keep the diet simple, nothing fancy.

PS: See if you have the option of getting a refund for anything unopened.