Hefe's are notoriously short lived. I have one that is a little over a month old. At two weeks it scored a 40 in a local comp and had incredible banana and clove aroma. Last night, only a month later, I feel like this charechter is already falling off.
I haven't ruled out changes in carbonation and the pour as a potential reason since I have been tinkering with my draft system, but still, just wondering what others experience.