Wow, I had to take a second look, Crowntails are so good at hiding their fin damage
Anyways, do you have any "Stress Coat"? If not, purchase some! It's a water conditioner that not only removes
chlorine (and if you get "Stress Coat +", then it also removes
ammonia), but also reduces a fish's stress levels and promotes the regeneration of fins. All I have to say is keep that water very clean and add some stress coat every once in a while to help those fins heal up. My halfmoon is going through the same thing, poor little guys.