Hidden Purchases Are Unhidden

Whenever I download a song, I usually hide it after a few months when I've had my fill of it. So today I went back into my account on iTunes, clicked manage hidden purchases, and downloaded a song, and ALL of the songs I have downloaded in the past are showing up in my iTunes library. When I click 'Hide' on one of the songs, it will disappear for three seconds then pop back up. I've tried restarting my computer and force quit on iTunes, but nothing is working. How can this be fixed?