Crinkling?
They've probably all got whatever she's got, they're just not expressing any symptoms right now. Kind of like cold sores -- once you've got the virus, you've got it for good, even though you won't have a cold sore all the time.
Stress can exacerbate the symptoms, but I don't know...
Chickens can't get into a peach pit, only peck at the surface. Wrinkly skin is fine too -- if I had a peach with a wrinkly skin and no squishy bits, there wouldn't be much left for the chickens. XD
How much room can you spare, and what's the biggest run you can get with your budget? Currently we have 3 chickens in a ~6x20 run with multiple levels, and there's about three or four times that in garden space. Four chickens is the most we'd have.
Hard to tell really. How soon can you get a...
I think the manufacturers base their chicken numbers on how many chicken-shaped cushions can be stuffed into the box.
Do they ever spend any time awake and shut inside the whole assemblage?
Grapes are nice. In every pack there always end up being a few squashed or mouldy ones that you don't want to eat, so those go to the chickens. A cherry tomato is fun too -- one runs off with it and smacks it about on the ground, and the rest follow her and hoover up the seeds...