So I have these 5 gallon barrels. I had rum in them for awhile but then put in 2 different beers for around 2 weeks each. My third beer has been in around 12 days. Today, one of them blew the bung out and started foaming out of the top. The beer was approximately 2 weeks old when I put it in the barrel. It was fermented in a temperature controlled chamber at 66 deg. It has been in my basement which is around 60 deg for 2 weeks in the barrel. The beer tastes fine. Is this an infection or maybe some minute temp change caused some additional fermentation?