It appears like they’re missing some scales? Is there anything they could’ve been caught up in or trapped into?
Or what’s the male to female ratio? Have you noticed aggression?
If you have no plants or invertebrates....
I’d add some pure sea salt (grocery store in a grinder usually with NO iodine) and dose a TEASPOON per gallon to start. It’ll help prevent infection and irritate their slime coat which is a good thing since it’ll help them produce more slime to heal faster!
The only plants that can bear salt in my experience is bamboo, anacharis, Marimo moss balls, red mangrove