That bad tone day was ROUGH.
The hardest part about figuring out your tone on a bad tone day is getting over the feeling that EVERYTHING you're trying feels alien and weird and not at all what you're used to feeling on the flute. You try what feels right, and it doesn't work. You try an extreme of what's right... and it feels wrong, but sounds right.
It turned out to be a great experience though, because I had a light bulb moment about what could be happening with some of my students. I realized I had COMPLETELY forgotten about my teachers teaching me to drop and relax my jaw. It had become so normal that I took it for granted! I've already started to make the rounds with my students now concerning this issue, and I'm excited to see where this takes us.
The only bad part about bad tone days is the tone. More good came out of this than bad, and I'm good with that. :)