Thanks for the responses! One weak link might be our fermentation vessel. We clean it and then sanitize it with iodophor every time, but we haven't taken it completely apart and sanitized all of the parts. It's a 15 gallon keg, so taking apart the in- and out-fittings and sanitizing them...
I've been having a curious problem with my beer lately: all but one of my last 6 batches has developed a sour taste within a few weeks. The strange part is that I brew 10 gallon batches with my dad, and after primary we split it into two five gallon kegs, one of which stays with him and the...