Ok, so I brewed my second batch of allgrain yesterday- 8gal. of an Irish Red, and everything went like it was supposed to. I cooled it to 70 deg. before pitching the yeast, and the carbuoys are in a dark corner of my garage which stays between 62 and 68 deg. at this time of year. I split the batch evenly and put 4gal in each of two 5gal glass carbuoys. I figure with that amount of extra space in the carbuoys it would be allright to just put airlocks in each. I go to check on them this morning and I see what appears to be a (for lack of a better description) a vacuum being set up in the airlocks/carbuoys (the water "barrier" being sucked back up into the airlock). Any thoughts on what's going on?