3 of my girls have small thinned patches of feathers on their chests. Not quite bald but thin. it looks like there's some dirt around the ends of the feathers. One of the 3 has lost most of the feathers on the back of her neck. I've been looking around on the internet and haven't really found anything that totally fits the bill. I can't really handle my chickens so I haven't gotten a good look at them. I can only do that at night when they're sleeping. I was planning on getting a good look tonight. Egg production has only slowed by like 1 or 2 a day. Its summer here and the humidity is high. Its not quite 100 yet, but is fixin' to be soon. This is my 1st summer with egg layers. All of my birds have their own field to free range in, its almost 1/2 an acre and full of grasses, no dogs or cats in it. Does the heat effect egg production and feathers or is this a parasite issue? Should I quarantine them now or wait until I have more info? Thanks so much!