How old are your birds?
Older birds (3 is old) slow down their egg production,
but not a drastic drop like you cite.
Are your birds confined to a coop?
If they Free Range, the whole flock can decide they have found a better place to lay some place else. If your birds have access to dense underbrush or briar thickets, these new nests can be hard to locate.
We live adjacent to a National Forest,
and there are plenty of predators,
so we built a Ft Knox Coop where we count them,
and lock them in a sunset.
Ft Knox Coop is surrounded with a large chicken wire enclosure that would stop or slow down a daytime curious dog or other predator.
We let our birds out of their coop, and into this well mowed and maintained area in the morning. They still have access to their nests in the coop,
and most are finished laying by 2:pm.
We then let them out to Free Range where ever they wish to for the rest of the day,
and we are in the area, usually working in the veggie Garden or somewhere else close by if anything happens.
When we suddenly notice a drop in egg production that radical,
it usually means a big Black Arkansas Chicken Snake has moved into the coop,
and is hiding under the hay somewhere. We've caught some that were 6' in length,
and can easily eat a bunch of eggs. They will swallow the eggs whole,
and even eat any ceramic or wood Fake Eggs you might be using.
If something else is eating the eggs, you WILL be able to find some remnant pieces of egg shells,
or a sticky egg wet spot where they had their meal.
As someone above pointed out, egg production stops during molt,
and it will take about 6 weeks before you start seeing eggs again.
This usually happens in very early Fall, so it seems a little early for that,
but its possible.
You will know if you have a broody hen (wants to be a mother).
She will go into something resembling a trance, and will seldom leave the nest.
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