Your best bet is to put the infected fish in a 10-20 gallon hospital tank and treat them there. QuICK Cure will stain your silicone. After the fish are being treated in the hospital tank, you can turn the heat up (plants will be fine, unless you have difficult-level plants) and let the Ich parasite die out, since there is no host in the tank.Is QuIck Cure safe on plants? I don't want to do salt in my tank because it is planted and I don't want to hurt the plants.
I do not know for sure if it is safe for plants, but there is no reason to risk it. Do the above and you will be much happier.