I also used to be excellent at spelling in school, however have since went downhilll and getting worse every year.

These are some words I have a hard time spelling, and if they are spelled correctly it's purely coincidental!

Diarrhea
Chihuahua
Muzzle
Dachschand
Rottweiller

Most of them are words I have to write at work and it bothers me that I can't consistently spell them correctly because it's on a medical file and should be spelled properly.