My 8 month old bantam cochin pullet seems to be going blind, There is no swelling, discharge or irritation of any kind. The past 2 nights she will not go to roost with the others. She stays on the ground. When she eats, she pecks but misses the food by an inch or two. She is also having a hard time drinking, finding it. She gets close to it and will eventually find it. So she does have partial sight for now. No injury that I know or can see. Could it be some kind of vitamin deficiency? Any ideas? Thanks.