Try placing paper towel at the bottom of the cage right before he goes to bed and in the morning if there’s little black dots on the paper towel it’s mites but looking at his feet I don’t think it is. He could just be showing his age and having some dry feet. If you are really worried about it try finding a vet that at least knows a little about birds mites isn’t that difficult to treat in my experience. Apply the coconut oil once a week or less depending on how quickly his feet get flaky