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lol. I was farming all day. Some of the best chickens I've ever raised were hatched in October after the moult, but I honestly don't care for July-August hatched chicks. 
They usually do just fine; they just turn out smaller. 
I have often wondered why. Here's my theory. The hens have been laying now for months. They have laid themselves silly since Jan or Feb. These last eggs are from bodies that are strained due to the excessive laying and the heat. Plus, the cocks are not as active in the heat; so, many of the eggs were fertilized by old stored sperm held by the females. Thus, the chicks are smaller and weaker than their earlier counterparts. That's just my thoughts.
By comparison, the child of a 20 year old is often more vigorous and healthy than say the baby of a 39 year old. The older the woman gets the more incline the babies are to be developmentally slow. Young women have healthier babies. 
If a hen has laid say 150 eggs or more by now; well, I think that just takes a toll.
Nothing to back up my theory other than observations. Sometimes we misinterprete what we see, but I think I'm right on this one.