If it’s not gapeworm, it could be
aspergillosis. Is their coop ever damp? Is it well-ventilated?
If it is aspergillosis, unfortunately there’s no treatment but removing them from the environment with spores can help. Maybe try keeping your two that are showing symptoms inside for a few days to see if they improve? And it might be worth going ahead and treating them for gapeworm, just in case. Hopefully
@azygous can weigh in on whether they’d recommend that or not.
I truly hope both these hens make it, but I would go ahead and figure out the process for having a necropsy done if one of them dies. It looks like the University of Missouri will do it. Then you’ll know for sure what’s going on and be able to help the rest of the flock.