White spots on fins?

[Singlefin]

I have a copperband butterfly that's been in qt for 4 weeks or so now. It developed white spots on its fins. I've scraped them off with my finger. They felt kinda hard. There's no spots on the body. I freshwater dipped before I added it. Treated it with copper for 3 weeks, para shield, freshwater dip, then a week of instant ocean lifeguard. It's now in saltwater with no medication. It's eating live brine and black worms vigorously. A little frozen. I'm thinking it's not ich. I've changed 50% of the water every 3-4 days. Last two changes were 100%. Scrubbed tank clean then refilled. Any ideas? Thanks.

 

[Deinonych]

Likely lymphocystis, a viral disorder that will go away over time with proper nutrition and water quality.

 

[Singlefin]

Thanks. I just stopped medicating it. Don't want to subject it to unnecessary stress and harsh medication if it doesn't need it.

 

[MrTuskfish]

Thanks. I just stopped medicating it. Don't want to subject it to unnecessary stress and harsh medication if it doesn't need it.

You've already done that, but most butterfly fish handle copper very well.