Hi, welcome to the forum.
The most common reason for hens to not be laying is the molt. At that age and especially if you are north of the equator that's not likely, but are you seeing a bunch of feathers flying around? Never say never. But the molt typically doesn't hit all of them overnight, it's more gradual. I guess that is a question, how sudden or gradual was this?
Another common reason for them to appear to have stopped laying is that they are hiding a nest on you. Two or maybe even three hens maybe, but not that many. Highly unlikely but never say never.
Has anything happened to stress them? Running out of water for a day or more, remodeling their quarters, moving them, adding or removing flock members, change of lights? Change can stress them which can affect their laying. They are especially sensitive to light, that has a direct affect on their laying. Have you recently turned off a security light or something like that?
Something may be getting your eggs. Most critters that eat them leave signs, broken egg shells or wet spots. Chickens might clean up the egg shells but they are generally not that good at it, especially that many. The only critters in North America that I'm aware of that don't typically leave signs are snakes, canines, and humans.
That's not a snake, I've dealt with them before. A snake eats a few eggs, how many depends on its size, then it disappears for a few days to digest them, then comes back for more. If it's every day it is not a snake. Besides, a 5' long black rat snake was eating 4 at a time and leaving the rest. I don't know how big a snake would have to be to eat 6 at a time.
A fox or coyote would probably be more interested in your chickens than the eggs, one of them is not likely. Dogs however will sometimes eat eggs but not bother the chickens. Do dogs have access? Since I don't know where you are I can't talk to other potential critters.
I'll let you decide if humans could be responsible.
It's possible a disease could cause that but if they are acting normal I really doubt it is a disease.
So what can you do? I don't know how you manage them, do they free range or are they confined to a coop and run? If they free range you can lock them in the coop/run for a few days. If you start seeing eggs either they are hiding a nest or you locked out an egg eater.
You can take a couple of real eggs, subtly mark them, and leave them down there. If they disappear something is getting the eggs.
Other than that I don't know. Just be patient I guess.
Good luck, this can be really frustrating.