Given that he is a beautiful good quality well bred boy it would be worth (in my own personal opinion) to take the option to use furan 2. Remember that furan 2 is a known cancer causing agent in mice and handle accordingly i.e. try not to touch. It used to come in capsules, now comes in plastic packs which makes it much easier not to touch. One course of 4 days should do.
I can see the white edges, can you see any pink/red lines up above these as usually they appear and then the fins/tail fray back to this edge and then it happens again and again. However, in saying that when the fins and tail grow back the new growth comes through clear, then whitens and eventually colours back up. However this does not look like new growth as it normally starts at the end and works back up, not around the edges.
I've had this happen to a couple of my breeding males (in individual tanks, each tank unfiltered) in the last week. Looking stunning one night, the next morning literally no tail. In one case the fish was like yours but black/green with red and in the other pure red. Never before have I had two fish go down with it together :evil: