Are you feeding the tangs dried macro-algae sheets? If not, you should, as Tinker's need macro-algae-based food as a large part of their diet to thrive. I'd also suggest adding a refugium to your setup, as the Tinker's especially are browsers on micro-crustaceans that the refugium will continually supply. In a refugium you can grow live macro-algae to feed to your fish.
I kept a specimen for about seven years before it passed. I discovered for optimum health and vitality they need the greens in their diet. I got the best results with the fish with 60-40 greens to meaty foods. He really liked green algae on stones the best.
Oh, and great photos. The Tinker's really looks in good shape.
And you know, that you're over the hill, when your mind makes a promise that your body can't fill . . .