Thanks for response, Masher.
Yes they've definitely been exposed to sunlight, a lot, I thought they'd been hardened off, BUT...
I'm thinking (& hoping!) you're onto something with the coldsnap thing. These plants are still in Solo cups, but I left then on my deck over night for a few nights, and the most recently of those nights, it poured down rain AND the temp does week into the 40s°F. And it was like a day after that I noticed these markings/symptoms or whatever.
Most of the afflicted plants are child that I was going to give away. I don't want to give anyone a virus, though. I'll hold off a few days and see if the symptoms spread or change, and offer more clues.
But yeah I never even thought the cold snap could be a factor.
Fwiw, I have seen plants with mosaic virus before, and this looks different... But I know there are different forms of MV. And my neighbor smokes like a chimney so I know that can be a factor....
I'm hoping this is just weather-related damage, and thanks again for cluing me in the temp changes, Masher... I'd still love to hear any other thoughts/theories from other growers.