First, some reasons you may think they are not laying, whether they are or not. I'll mention several things as you are looking at them and I'm not.
The molt - I know, fall and winter is when most chickens molt but some can at other times of the year. A common cause is a change in light pattern that causes their bodies to consider that day light is decreasing, not increasing. That could be a security light that burned out or you changing their lighting. But stress can sometimes cause them to go into a molt out of season. Are you seeing feathers flying around?
Hidden nests - I've had hens stop laying in the nests and start laying somewhere else. They can hide a nest really well in a coop and run, it doesn't always have to be while out free ranging.
Egg Eating - Many critters like to eat eggs. Some leave signs behind like egg shells or damp spots but some don't. Snakes swallow an egg whole and could be more active now that the weather is warming up but I don't think it is snakes. They eat a bunch of eggs then disappear for two or three days while they digest them before coming back for more. Besides, a single snake can't eat that many eggs at one time.
Canines swallow eggs whole. If it were a fox or coyote they'd probably be interested in your chickens more than the eggs so probably not them. But a dog may leave your hens alone and eat your eggs. Does a dog, especially a big dog, have access?
Humans do not leave any signs when they take the eggs. Often when this happens it is not a stranger as a stranger would not have that good of access.
Change or stress - Chickens often do not like changes but can be adaptable. A change in the pecking order, adding or subtracting chickens, changing accommodations or nests, a change in food, a change in weather (usually extremely hot or extremely cold), many things can cause them to temporarily stop or reduce laying. Changing the bedding material may be a cause, either to reduce laying or to change to a hidden nest. These can all stress them.
Predator attacks (whether real or perceived), can also stress them. Running out of water can have the effect you saw.
Diseases can cause them to stop laying. If they are acting healthy this is probably not it. Some diseases cause them to lay deformed eggs.
So what can you do? If they free range, can you lock them in a secure coop or coop/run for a few days to see if the eggs increase? This could mean you are keeping them from hidden nests or locking out an egg eating predator.
Discretely mark a couple of eggs and leave them down there. If they disappear you'll know something is getting them
This kind of thing can be extremely frustrating. Sometimes you just can't figure out what is going on. It can be hard to be patient. Good luck figuring it out.
