Probably just lock down like usual, and hope for the best :idunno
If they are behind on development, they may hatch a bit late. I have read that turning is most essential early in incubation, and not really at the end, so locking them down on time should be fine even if they do hatch later than...
If they are all like that, then either they are all fine, or they all have a problem. Either way, there isn't much you can do, considering that each chick is inside an eggshell where you can't get to it. Just continue to provide the right conditions and hope for the best.
Chickens do many weird...