It could be a lot of different things or maybe a combination of things. The high heat is definitely a possibility.
A very common cause of hens not laying is that they are hiding nests. If they free range, oh, boy, good luck! But they can be pretty creative hiding a nest in the run or coop.
Some hens lay almost every day, some not so much. It’s not that unusual to get quite a bit of fluctuation if you have hens that lay every two or three days.
If your hens laid throughout the winter, with or without extra light, they may just be burned out and needing to rest. Commercial laying hens go through a laying cycle. They ramp up to top production pretty fast once they start but then gradually drop off in production the longer they lay. Usually after about 13 to 14 months they are down to about 60% of peak production. They may go through a mini-molt to rest before they resume production.
I don’t know how long ago you did those integrations but that can throw them off for a while. It may even cause enough stress to kick off a mini-molt. Running out of water for a day, changes to coop or run, changes in feeding, just about any changes can kick off a mini-molt if it causes them stress.
It’s always possible that something is getting some of the eggs. Many things will leave traces behind but some things will take them and not leave a clue. Possums, skunks, raccoons, rats, or even the chickens normally leave clues.
A snake does not leave a clue but they are inconsistent. A snake will show up, eat however many eggs he can hold, and leave for a few days while he digests them. Then he returns.
A canine will eat eggs whole. You’d think a fox or coyote would be more interested in the chickens but a dog may very well eat eggs and leave the chickens alone. Do you have a family pet that has found out the egg song means a snack?
A human will not leave a clue.
What can you do? If the hens free range try locking them in the coop or coop and run for a few days if you can. If you suddenly get a consistent increase in eggs, then you know they are either hiding a nest or you locked some egg eater out.
Try putting a few marked eggs down here. If they disappear you know something is getting them.
It’s probably just the heat.