i had the same problem here in sc bought a nuc and started feeding 1st of june...they would consume a quart a day. put them in a deep hive body with 5 frames filled comb and five of foundation...even with the feeding they were slow to build. inspection showed queen laying, capped brood, honey, and the like...yet still they were slow to add new comb...weeks later upon inspection i found a queen cell that was opened found the queen( wonder if they superseded her)...well anyway the intake of 1/1 slowed down dramatically...and i discovered we have a cotton flow going on now....and they just took off ballistic...building new comb now....just added yesterday new deep hive body and placed a frame from bottom to top and this morn they are building in top box already...and i was ready to give up?
i would suggest if no flow going on there keep feeding they will let u know when they prefer something else to take in
good luck