My advise is, if there is fresh blood and veining, this ALWAYS means they are not ready and are absorbing, keep a close eye on this chick. You have already found the assist article, breath and re-read the process the chick is taking inside that shell.
Have ready for its hatch some dental floss, iodine if possible. I use umbilical veterycin spray gel on a open navel if I get one.
There is a process each chick goes through for hatch, they simply do not start zipping until they have absorbed and the time is right. Remember a chick will first internally pip and them externally, sometimes this is at the same time, HOWEVER, there is a long rest period before the final 15-60 minute actual turning inside the shell zipping to release from the shell (hatched). Most times its our panic in assisting that does more harm than good. Any time a chick escapes the shell before absorbing they will have issues and in a lot of cases death, if not right away in a few days thereafter. Anything could be going on in that egg, but no matter what it will absorb, and if something has stopped its ability to do so, it will simply die and there is nothing you can do about that. You need to watch for the veins to recede.
You may need to refer to the hatching 101 article at the bottom there are electrolyte recipes, and chick orthopedics.
I wish you luck with your babies!