see, thats the thing, the corks were being pushed out seconds after being bottled, not just overnight, and the worse ones were the ones slightly more filled than the others, that's why I'm assuming it's simply the air in the headspace being compressed, and pushing out the wet cork.
Dude, you've got secondary going on, and a lot of people pointing it out in very polite ways. Your mead was in the process of degassing and still fermenting when you were bottling which is why you had an immediate push out of the corks. Handling, racking and bottle filling all agitate the mead enough to cause significant enough off-gassing to push out your corks almost immediately.
Remember that sorbate and sulfite additions are not a completely sure fire way to stop fermentation which is why commercial meaderies and wineries use filtration, cold stabilization or extended racking and aging to ensure a complete cessation of fermentation.
Save yourself some grief and get them out of the bottles and back under airlock, especially if you plan to give any as gifts or send any to friends. Last thing in the world you want is to have one blow up in a friends face, in transit or in your face.
Cheers, and please take heed of the advice given here,
Oskaar