First, you don't need to disclose any of this, but if you're in the U.S. and the appointment was Wednesday, maybe she was up late watching election results? (My H and I both were, and my T looked a bit rough that day, too--we talked about the election quite a bit.) And perhaps she overslept and didn't have a chance to apply makeup. Just thinking of something that wouldn't really involve her own well-being. Or she may have slept poorly for other reasons, perhaps something fairly benign in the big picture, like heartburn.
This has happened to me before. With my current T, there was a time maybe 2 years ago when he had to switch to virtual at the last minute with no explanation (he said it wasn't Covid-related), and he just looked sad to me.
I didn't mention it at the time, but I ended up emailing him about it, saying I hoped he and his family were OK, as he looked sad. He didn't respond to the email (well, he did confirm receipt when I asked him later, hours after the window when he normally responds). He told me he was a bit confused about what I was asking, or something like that. But he's also someone who doesn't like sharing personal stuff unless it's on his terms (like if I ask him, he might not say, but he might volunteer something on his own).
With ex-T, there was one time when she just seemed really sad. At the time, I said to her, "You seem sad," and she said, "It's been a sad day." She didn't elaborate, but I assumed something personal was going on. It helped to hear that it wasn't just in my head.