You were spot on about the incubation. Thank you. My first hygrometer was 10% too high. Better eggs next time I start.
Meanwhile I assisted the last hatch (4 of 5 araucana chicks) and am planning to assist the next as these air cells are still well below norm. Will lockdown on day 19 to give the best chance for those that are closer to normal development a go without assistance in a second incubator. The rest I will assist as soon as the internal pipping is apparent.
It can take up to 12 hours from internal pip for a chick to pip externally. And that is completely normal.
It isn't until after that external pip that the blood vessels start to recede the yolk absorbs. Vessels need time to recede before you assist or you could kill the chick. Also keep in mind that hatching can take anywhere for 12 to 24 hours after that external pip. If a chick can breathe (cheeping), there is no rush to get it out right away. Just keep an eye on them. If you notice a chick pecking like crazy and getting nowhere after an hour or two, by all means help. But if a chick never manages to pip externally, odds are something was wrong with that chick in the first place.