There are several things that can cause your egg production to drop, but if you are getting the same two hens laying every day like clockwork, you can discount most of them. Nothing is taking or eating your eggs.
Sometimes hens will hide nests if they can. That’s one of the biggest reasons hens “quit laying”. They don’t actually quit, you just don’t know where they are laying. With a drop like yours that doesn’t sound likely, but it is a possibility. That’s a lot of hens to start hiding nests.
Change and stress can cause some hens to stop laying for a while. If you change the pecking order by adding or taking away flock members, moving them to a new coop, if they run out of water for a while, a fright from a predator, lots of different things can cause this stress. But if it has been two weeks, this is not likely. Some of the brown egg layers should have started again by now, though sometimes that stress can help trigger a mini-molt, which would last longer.
Sometimes chickens will go through a mini-molt about a year or so after they started laying and stop laying for a while. They are not all consistent as to when this happens but sometime around a year is pretty common.
How old are yours? Often a pullet will continue laying through her first fall/winter and skip the big main molt until the following fall. Not always, but often.
You asked for thoughts. Those are mine. But what I think is really happening is that your hens are molting because of the days getting shorter. Some hens are fast molters and drop the feathers in bunches. They look pretty ragged. Others are slow molters, gradually losing feathers. You can’t really tell if they are molting other than you see a lot of feathers laying around.
Sometimes hens will reduce or stop laying when days get shorter, but that is practically always associated with a molt. The length of days is more likely to affect when they start laying after a molt. Some will crank up laying again as soon as they finish the molt even in the middle of December, but a lot will wait until the days start getting longer.
