I'm not sick, but I have had to lower the keys on several songs if I want to reach the high note at the end.
My Way, from C to Bb, Unchained Melody from G to F, Only Make Believe from C to A and Bb, I Will Always Love you, C to Bb, etc. Most nights I COULD still hit the high note, but I don't want to take the chance of trying and not nailing it.
You know what, it sounds just as good in the lower keys. Nobody knows the difference, and it's easier on the vocal "chords".