I thought the same thing. And I was there! - not (yet) a big fan at the time, but while the music and singing were on point, some energy seemed to be missing... And watching all these exellent videos from this concert - look in her face, the eyes, the smiles, the movements. She tries, and there is nothing missing - but we know this is like bare minimum for her. Tired or distracted or unwell would be my guess too.
