If they are in the shell for a while trying to hatch, it can put pressure on the neck and head and in silkies, especially, that can cause wry neck. It can also be caused by a bump on the head.
If it makes you feel any better, I had one silkie chick that developed the same issues after getting pecked on the head. It took about a week, but eventually she worked it out and is now 9 months old and running around out in the chicken pen with the others.
She still has a 'tic' from time to time where she jerks her head from side to side but she gets around just fine.