I have one little four week old chick that looks like he has crookneck. He seems to only be able to look straight down when he stands erect. Now if he is bent over, he can lift his head a little. It is odd for sure. I am giving polyvisol in their water and changed their feed to non medicated. He has been this way for three or four days. How long does it last, or at worst, how long should I wait for it to clear up before having to cull it? Thanks!