I have a YT that had really bad fin rot but it went away on its own. The fins were mostly gone. I didn't think there was any chance in the fins growing back. After about 5 months with him back in the display, he made a full recovery. As far as the worms I suggest metro.
I have a wrasse in QT now that I have in copper and it previously went through 3 doses of prazi, still with the white stringy poop. I just got done with 5 feedings (one a day for 5 days) of mysis soaked and frozen with metro. I he seems to be eating better now but I haven't seen him poop yet so I can't say really if the worms are gone.
Someone also suggested paracide x although I haven't been able to get through that sites check out so I haven't ordered that yet but it seems like it should be a good product to keep on hand.