I have a (approx) 4 day old crested pekin duckling. One of its eyes seems smaller and doesn't open as wide as the other eye. This duckling is smaller than the other two I have that are supposed to be the same age. The other two are different breeds, Crested Black Swedish and a Cayuga. I am wondering if I should be concerned about the eye. The duckling seems to eat and drink but isn't as active as the other two... any thoughts?