why not separate this ill bird (NOT using straw > use cardboard sheet to line whatever yo separate him to and perhaps a couple sheets of newspaper on top of that (easy to just remove a sheet daily).
Here is an online source of the vitE/selenium > I put a geltab in with a bit of cooked oatmeal...
I dont find much basic info (housing/weather conditions (has it been wet/raining there?) / treats (chick and make sure NO salt!) what for bedding material do you use?
When you have a bird with a crook neck symptom it can be from several things... even when there is not a deficiency per se of...