Nope. more than likely the fact that some gushed and some were under is really just because they're just on the cusp of being ready.
Inconsistant carbonation, usually simply means that they are not ready yet. If you had opened them a week later, or even two, you never would have noticed. Each one is it's own little microcosm, and although generally the should come up at the same time, it's not an automatic switch, and they all pop on.
A tiny difference in temps between bottles in storage can affect the yeasties, speed them up or slow them down. Like if you store them in a closet against a warm wall, the beers closest to the heat source may be a tad warmer than those further way, so thy may carb/condition at slightly different rates. I usually store a batch in 2 seperate locations in my loft 1 case in my bedroom which is a little warmer, and the other in the closet in the lving room, which being in a larger space is a tad cooler, at least according to the thermostat next to that closet. It can be 5-10 degrees warmer in my bedroom. So I usually start with that case at three weeks. Giving the other half a little more time.
If you watch Poindexter's video on time lapsed carbonation, you will see that in many instances, before a beer is carbed it my gush, that's not from infection, or mixing of sugars, but because the co2 hasn't evened out- it hasn't been pulled fully into the beer. Think of it as there's a lot of co2 being generated and most of it is in the headspace, not in the beer, so there's still "over pressure" in the bottle, so it gushes when it is opened.
But when the beer is truly carbed it all evens out, across the bottles.
Video Link: http://www.youtube.com/watch?v=FlBlnTfZ2iw
You just caught some before they evened out, and others had. The 3 weeks is kinda just an average, some take longer some sooner.
But I really don't think its infection. This has happened before but not to this degree. Thanks as always..
