Have a think about it - you are using 14X12 deep national brood box---how many frames are fully drawn?---how many frames with brood?---how many seams of bees?----how many are store?Thx
Think if I give them some 1/1 SW they will be stimulated into drawing out some more comb?
On top of that you have a super partly drawn? and filled with sugar syrup?
When do the bees slow down production and when do they begin winter preps?
Have you removed that second super yet ?