I agree it is overwhelming and confusing. With the symptoms they are experiencing according to what I read on the internet and BYC, it could be a number of things (injury, Mareks, Botulsim, etc).
I have a 3 mos old chicken with similar symptoms. Did a lot of searching on the internet and this website. At first I thought it was Marek's or botulism, but its been two weeks and she's still alive and doing a little better. I think she has limberneck, or crookneck. ( See information...