You can hear it in I Choose. He had trouble hitting the high notes. He was also sick during the Much Music in Canada event and The KROQ Weenie Roast of 2012. He sang better at other shows, but he was still amazing during the shows when he was sick.
During the much music I remember he being sick. But if he can't catch a note it doesn't mean he's sick. I choose has a damn high note to reach and I dare you finding a video where he sings it perfectly Don't get me wrong he sings well but in studio he does things that live are hard to do because he's singing every day for more than an hour. He can't sing well the highest parts of hammerhead for example or yggfk.