I have an incubator hovabator. I have successfully hatched four chicks. But now since then the rest that are hatching are pipping externally then that's it. They are having that shrink wrap happening to them. I increased my humidity to 70 the first four wer at 60-65 humidity with no problems. Also it seems like they may be hatching a bit too early not too much but thy are not like the four. The shrink wrap---seems like some tiny but of yoke left----and just smaller wings. What can I do?