Scratch grains and other "treats" like watermelon and such can diminish your protein level too far, especially since layer is only 16% which is the minimum suggested for light breeds like leghorn... and maybe your calcium level if you don't offer OS on the side. Scratch grains is often 8%, depending on the ratio you are using... you can see where you might run into some issues including reduced laying and feather pecking. Heat does have some impact, and that may be it. But if it's seasonal then you shouldn't see a sudden drop in production. Hey, maybe a perfect time for you to try fermenting your feed... it will easily increase moisture uptake and not have to take in moisture to wet the feed. Plus the benefits are huge. The one that made me stick with it is the difference in how less offensive the poo smell was!

It doesn't really take too much extra effort once you get it figure out. Check the link in my signature for quick facts. If nothing else, and you truly think moisture is part of the issue, soak you feed and see if it helps. (I still remember you are busy)
Personally for breeding I feed 20% protein flock raiser with oyster shell on the side. It has been shown that higher protein feed (the amino acids there in) actually gives better hatch rates and viability to chicks. (can go find studies if you care to see them) Not knocking those who feed layer and hatch all day long. Too much OS, as in layer feed *can* (doesn't mean will) cause kidney issues long term in non layers like broody's, roosters, chicks, molting hens, or growing birds. Since I always have broody's, chicks, grow outs, and roosters... there is NO way I'm feeding separately.
That being said, my birds are free range and I have no control over what they eat. The 20% gives me a little wiggle room without worry. And most of my birds are heavy breed/dual purpose. It's enough for chicks without being too much for hens. It's a happy medium, not perfection. Scratch is candy bars and should be fed at a rate of no more than 10% of the total daily ration. Or better yet, avoided all together, it wasn't even cheap last time I looked at it. And people think they are doing their birds good when they feed lettuce and such, but it is high bulk low nutrient so in fact doing the exact opposite of what they intend. Yes I still do watermelon, cantaloupe, or whatever refreshing things... frozen peas are a great source of protein!!! People will freeze peas, corn, carrots, chunks of grapes or whatever in a larger hunk of ice that melts throughout the day as they peck down to it. Bonus, free enrichment for the birds and a refreshing, nutritious treat that goes farther while increasing hydration.
Sorry for going on and on!

Nutrition is key for many things.
ETA: it is my understanding that heat can make for softer or brittle shells.