Forgive me, but I don't see a crooked neck in the picture---can he not lift his head above that position?
You may want to try giving him some electrolytes in his water. Chickie may grow out of it, or he may not. In the meantime, the electrolytes will help give him an "edge" if he is not growing as quickly as the other chickies.
are you saying the little guy's neck goes off to the side?...if so, that is 'wry neck'...it's like a stiff neck in a person
only worse... torticollis is another name for it...
I had a duck that had wry neck...he couldn't swim due to it but he could do anything else. don't have him anymore
as a predator got him but he had quite the duck following until then.
I had a chick with wry neck once. Get her some PolyVisol without iron. It is vitamin drops for human infants. It worked wonderfully for me. I gave a drop twice a day. Next day she was fine. I learned this on BYC. I think the bottle cost around $7. Good to have around.