Well, two days later, the last one finally hatched. Posted a 5 min video of the hatch here and a short one of the four chicks here.
So, after all, we had 100% hatch rate of the eggs I brought in. BPR was originally sitting on 6. One clearly was not developing and I took out at about two weeks. One was broken open by mama on day 17 at which point I brought the other in and put them into a hastily-purchased Little Giant. I'm thrilled that every last one of them hatched.