Andy,
Welcome to the board, though I'm sorry it took a sick fish to get you to post. Please check out this thread and provide us with additional information as requested:
http://forum.simplydiscus.com//index...;threadid=1082
In the meantime, I would suggest increasing your w/c on the q/tank to 50% daily. No matter what the problem is - bacterial infection, fungal infection or parasite, clean water to prevent secondary infections is key!
Give us some more info to work on and I'm sure someone will be able to help!
Thanks!
John