I'm surprised if 2 caps that they shipped you from the factory are that far apart.
As a reference, I have two AT853 card caps where they are from 2 different ebay deals, physically look different, probably years different manufacture, came on bodies where one had thick wire and the other had thick wire, connected to 2 different types of phantom adapters... in other words, they didn't even pretend to be a closely related... and they are about 2db from each other. Shit luck? Maybe. I thought probably all caps produced in the last 10 years are probably within some half decent relation to each other.
I have several sets of AT853's and caps and I've never seen a pair that were noticeably off other that the above really mis-match pair. I have one body on one of my sets where something is funky with the body and sometimes it's off several 5 db, then I unscrew the cap a little and tighten it back up and it's dead nuts. Just dirty I figure. I've never bother to take it apart.
I'd suggest you check them on someone else's bodies, some one else caps on your bodies... if it is real, then I'm surprised.