Mandarin dorsal fin damage?

[Wicket30]

I just noticed the tip of the dorsal of my mandarin has gone white. Is this something I need to treat or is it just physical damage? Please excuse the algae I'm battling.

 

[Sharkbait19]

I can see the white area, but it’s hard to tell exactly what it is. Could you get a pic on whites with the fin extended.
Damage from injury is a good bet though.

 

[Wicket30]

I can see the white area, but it’s hard to tell exactly what it is. Could you get a pic on whites with the fin extended.
Damage from injury is a good bet though.

Thanks, I'll try, but he doesn't extend it often.