oh joy!

Adderall may have a drying effect on vocal fold tissues, which can lead to hoarseness, soreness, voice changes or laryngitis. Additionally, dry vocal tissues may be more prone to injuries such as nodules.

found here

I was listening to last week's lesson yesterday and was really annoyed by it. So today I thought I'd work the same song and see if I couldn't fix what I thought I was hearing and just wound up getting even more frustrated (high G should not be a problem. ever.) anyhoo, this may explain it.