Do these birds look healthy to you? They are slightly larger than hatchlings, White Leghorns. They were at a local dealer last weekend, and dozens of them look like this.
It is hard to say just from one pic. From what I can see of the bedding, it looks clean. All the chicks seem to have similar bald patches. I'm guessing it's picking from being over crowded. Or, maybe they are just feathering out oddly. I have had chicks who sport bald areas for a short time.