Longest age for eggs was in the first hatch some would have been 7 days. I didn't go longer than that collecting before putting them in. All other ones I added were at most 4 days old when put in. But would being very cold affect how long it takes to hatch? Because some were outside during temps of 15-30 degrees until I could get to them. Anything below 15 usually vertically cracked before I could get to them. I tried to only grab eggs that were warm when I got to them. But who knows if one chicken laid them left them and they got cold and another went and sat on them for a bit.If you set older eggs they can hatch later but I don't think that's the case with yours since it has been multiple hatches. It really sounds like it's a low temperature thing.
The baby that pipped through the vein passed. The one on the right was ready and making a ton of noise so I helped it out. Belly is still a bit big but yolk is fully absorbed and it was ready. HUGE chick which is probably why it couldn't turn pip well.
The other chick is looking good but has a bit of veining still going to wait a while and check on it again before bed.