I had this same issue with one of my 1 week old Coturnix quail last week. He is doing fine, eating and drinking like the rest, growing at the same rate. After doing some research I found it could either be vitamin deficiency or an accident in the brooder.
But then in my new batch only 2 days old I noticed a chick lying in the plate that I use in the brooders for a feeder, with his neck hanging over the side. I am assuming that a nerve was pinched and this is the reason for a twisted neck, and sure enough the next day he had a bent neck. I changed out to a smaller, shallow feeder so it would not happen again.
Do you think my assumption is correct, that it could be an accident in the brooder, or genetic, or vitamin deficient problems?