Thanks, all.
Yeah, I could have called the vet, and would have, if I’d been more worried and it hadn’t been Saturday night. Jez was breathing fine and would stir if I poked her, but then go right back to sleep. She’s smaller than Zeb (4 lbs. vs. 5) so it makes sense she’d be hit harder. They did sleep in this morning (yay!), but are up and alert, if not particularly rambunctious, this morning.
I haven’t had kittens in almost 20 years, so I couldn’t remember if this was normal or not. I assumed it was something about the cooties in the vaccines working on them, but just had a worried mama moment.
Again, many thanks for the answers.