Hombre del mont
Dr of Stupidity
We don't have a green house but if squash plants are left out they get some PM.I would pay special attention to those cobs just in case. Big humidity swings like the one you described are really inviting to mold and other funghi, even more so than constant high RH. Do you usually have powdery mildew problems with your green house plants?
I've seen quite a few people on here making cobs without a vac bag and I did it once myself 35yrs ago, so I know it's doable. I think providing my material is on the dry side to start with all should be good.