Am I the only one who really can't recognize her in that video? Are you sure that's ayu?
In terms of her voice, though - I thought her voice was quite off at the CDL too, but honestly, it's not surprising since she just had a baby. Keeping your voice at the ready takes a lot of effort, and she might not have had the time for that with a newborn. As for right now, she might not sing much, because well... No concerts to get ready for - AND a baby (all things considered, I assume this is the best time corona could happen, since she gets to spend time with her family! Of course, hoping everyone's safe).
Also, her voice has generally been going up and down, and sometimes it's just better than others. Around 2008 when I got into Ayu, I watched the 2007-2008 countdown and I was baffled at how horrible she was live, lol (though a part of that was probably also getting used to her hearing loss). But the last few years, she's been AMAZING live. Back in A BEST era, she also had periods where her live singing was very nasal. I think it just changes all the time, and even from concert to concert. Not to mention, of course, small things like the common cold can do a lot for a period of time (like I assume she had a cold during the filming of Just the Beginning Part 3 - but that was imo one of her best concerts ever, so I won't mind another "cold concert"
).
Let's just hope it's not her hearing! She can go on for as long as she wants to with a "bad" voice, she's still popular, and playback is an option. But losing her hearing completely would be devastating.