Sick peppered cory! Plz help

[Strangeland9]

I have a ten gallon planted tank, it has been setup for a year now and is properly cycled. I had the levels checked last week and i was told they were perfect (haven't gotten around to getting a test kit). Anyways my oldest and favorite cory is acting very strange, very unlike his normal self. He is swimming around the tank sporadically and doesnt seem to want to be on the bottom, I also see him swimming vertically quite often. Any ideas anyone? I have never lost a cory before.