May have oversalted; water quality great, but bit of fin rot on guppy & fast breathing cory. Solution?

schoolmom asked:


I think I’ve added the right amount of conditioning salt to my 25-gal aquarium, but I mistakenly soaked a pouch of carbon in salt water and then put it in the sunshine to recharge. I rinsed it before putting it back in the filter. What should I do now?