Swordtail fin not looking well

[confusedman]

I noticed the Platy is nipping the Swordtail. Now the Swordtail fin is white and when I took the pictures I noticed it was damaged Maybe the bottom one is too. No idea if the damage is because of the nipping or if the Platy nips it cause its damaged.
Is there anything I can do?

 

[Hufsa]

I would say it's damaged because its nipped and not the other way around.
Sometimes you can get an unusually aggressive livebearer (fish) that wont get along. I would ask your fish store if you can return the nipper.
The one with damaged fins will likely heal well with no more nipping and lots of fresh water through waterchanges.
Keep an eye on it to make sure it doesn't get worse or the fish gets lethargic

 

[confusedman]

The thing is... the nipper doesn't show chasing or bullying... he gently goes and nip!! and he only does it to the Swordtail

 

[alto]

Decidedly not a “gentle” nip given the amount of damage - that is fin rays and not just fin tissue that has “gone”

Also looks to be secondary infections (white fluff), and the damage is very close to the body now which makes internal bacterial infection more likely to develop, also permanent damage to the fin - the swordtail does look somewhat “clamped” in the photos

(it’s also possible this began as infection and the actions of the platy are secondary - and definitely not helping)