internal pipping or shrink-wrapped chick?

I have some eggs due to start hatching tomorrow. I put them in lockdown yesterday (I know, a day late), and candled them before I did so. In more than half the eggs, the air sac was HUGE - but also not "even." Basically, it looked as if the air sac was enveloping the chick, hence why it reached down around the outside of the shell. The chicks in all of these eggs were still moving. The rest of the eggs looked "normal" - an even blob at the large end of the egg.

My question is - for these eggs where the air cells appear to have expanded down around the chick - is that b/c the chick has pipped into the air sac & the membrane has begun to retract? Or does it sound like the chicks are being shrink-wrapped inside their shells? I do not have a hygrometer, but I have never had a problem with humidity in the Brinsea Octogon Eco 20 that they are in, as long as both wells are filled at lockdown. Plus, it is humid as anything in the "external environment" (house). Thoughts? I don't want to lose these chicks to shrink-wrapping!