4-H Chicken Mom, you have a real mystery here.
Thinking out loud:
Since all your birds have stopped laying SOMETHING must have triggered
this in all your birds at the same time. That rules out disease or stress from
a fair. This points to something environmental. If they layed fine on your
current feed I would rule out nutrition also.
Fruit-Hey, the Meyer thing came from somewhere. Saying "no fruit" is
almost impossible since fruit varies so much un chemistry from one to
another. Maybe the cantaloupe triggered some kind of rare chemical response.
Sometimes the obvious is the correct answer. If I were you I'd be considering
the fruit also, as unlikely as it seems.
I'm really thinking about Rufus's comment. Animals sense things we don't.
Watch close for any clues.
I'm not sure how your weather has been but our temps have gone from
50 to 90 and back and forth a few times. We usually get a week of summer
weather in October but this year is strange.
Finally, one of my 9 laying hens went broody this week. Egg production for my entire
flock dropped in half. I'm thinking something hormonal is going on.