Had a brew on the go and everything was going as expected, the fermentation had slowed so that the airlock was bubbling at > 1min intervals, but after 11 days the fermentation increased to 2-3 second intervals. Brewing temperature has been consistent at 18-20 degrees C, so I'm not what could caused the change, any ideas? The brew's now on day 14 and fermention is not slowing, ideally I'd like to get the beer bottled but not sure whether it needs longer to settle down.