I'm not terribly clued in on all the physics and such at work i must admit, but i guess if the air in the jar is humid, and then chilled, it's going to dampen the bud. Just pondering here though.
Either way, from what i've read, the mould would be caused from excessive moisture levels in the buds or air. How dry are they, if you bend the stalks, what response do you get, is it bendy or stiff or does it snap?