+3 on continuing to treat for another couple of weeks.
In regards to CLs being more susceptible to Ich, I think it has more to do with their location in the water column than any sensitivity. Ich Spores fall off into your substrate and when they hatch into their free floating phase in search of a host, the loaches are the first fish they usually encounter. That's typically why catfish will be the most infested...really any bottom feeder will typically have the most spots in an ich infested tank.
In any case, keep up the good fight. Good luck!
