A 6 day cold crash at 37*F didn't drop enough yeast out to keep it from carbonating. I typically crash for 5-7 days at 35-36*F and the batches that I bottle carb turn out just fine.
This time of year, room temps can get down a bit below 70*F. Even a slight decrease below 70 means that it will take longer than the normal 3 weeks that it takes when stored at 70-75*F. Also, higher ABV and certain complex beers will take longer.
Did you use an online priming calculator? If so, what temperature did you plug in? What temp are they currently stored at?