I'm conviced it's a different fish. It might be the angle and size of the pic but his dorsal fin is competely different in the before and after pics.

If it was just a drastic color change, you'd still be able to see the red wash in the before pic as well. As far as I know, red wash never goes away.. even in stressed out fish it should still show up. Also, if he was stressed out before, his normal color wouldn't lighten up (when returning back to his normal color), it'd get darker and more vibrant if anything.