Did you recently add a new fish? If so, were they quarantined before you introduced them to your existing stock or did they go straight into your main tank?
I noticed in the pictures of your red isleta that it also appeared to be peeling and its eyes were cloudy. Now that you have a second fish showing signs of peeling, it's probably safe to say that you introduced something into your tank. This definitely doesn't look like ich.
You say your other fish are fine, but this is two in a row in a short time. It's possible that they're just not all getting sick at once. Sometimes it takes a while for the infection to spread.
I don't have any clue as to what it might be, but I think it's safe to say that you've got something in your tank. You can get an empty 10 gallon for $10 at Walmart and usually an empty 20 gallon at somewhere like Petco for about $20. All you need is a sponge filter and heater and you have a quarantine/hospital tank. I think that would be a wise investment for the future.