Oh chickabator, I'm so very sorry! HUGS AND THANKS for doing what you could. Sometimes no matter what we do, it just doesn't seem like it was enough, and we lose them.
My little guy or gal, Eeyore, is the same. Really looking at her, you wouldn't realize that something is wrong, other than appearing to have a short neck. But when you move those feathers back, the Z neck is still there. I have 31 chicks, from almost 9 weeks to 4 weeks, and none of the others are affected. I can't explain it either. Everything I read says vitamin defiency of one kind or another, but adding those still didn't improve her. I even started giving higher protein feed to see if that would do anything. So far, just the same.
I contacted VA TECH POULTRY dept and was told it could have been injury from vaccination, but I don't even know if they were vaccinated or not! It came from Mt Healthy, but I bought it at a local feed store, so no idea.
Eeyore continues to eat, drink, roost, fly, walk around, etc just like a normal chick. They only real difference I've noticed it lots of scratching at the ear. So I'm beginning to wonder if there is a tumor or infection in the ear, or that area that is causing this. I've going to attempt putting some antibiotic ear drops in that ear twice a day and see if it helps. Figure it can't hurt, and nothing else is helping....