DISCLAIMER: I'm a first year newbie myself, headed into my first winter....So, I have no experience what-so-ever. I'm planning on trying to take a little fall honey and reduce my hive sizes to get ready for winter sometime in the next couple of weeks.
However, I'm guessing that it could be that maybe it's a reduced flow, or just the fact that the girls know winter is coming and are being a little more protective than usual of their honey stores. I'd say suit up and get done what you need to get done.
Good luck! :)