I figured your been arround w/ 700 posts. Everyone gets to this point eventually if your in the hobby long enough, to be going 3 yrs w/o a problem means your lucky, good, or a bit of both.
I think if you have been arround this long, you will be arround for another 3 or more. If you think long term a QT isn't going to be a bad investment.
Freshwater dips are effective treatments for ich, and clowns are tollerant to them.
To preform a fresh water dip get fresh water (dechlor-tap is ok) to the correct temp, and pH and add the affected fish for a period of no-longerr than 10 mins. Keep a close eye on it to make sure it is not freaking out and breathing super fast. If so end bath early and test the water fro temp and pH.
This treatment need to be reapeated daily b/c it will only kill the paracites on the fish, which still leaves the ones in the substrate and the water.
This treattment usually works best in conjunction w/ qt-ing b/c it is much faster to catch them and less stressfull in a tank w/o LR.