Finally figured out that the hens are all laying in the coop and the broody ones are stealing the eggs. What clued me in? The fact that a hen I know I only left ~4 eggs under suddenly has 11.
So, grabbed a flashlight & some construction paper & made an impromptu candling box. 3 of hers are probably developed. 7 weren't, so I filled a bowl with water; only 1 floated, so that one got tossed & the rest are in the fridge.
Oh, you did the math? There's 1 missing?
Yeah. It's hatching. Along with 2 other eggs under 2 other hens.
(I candled all the other eggs too. Most are either far enough along to leave, or have shells so thick I can't tell.)