How many undrawn frames are there? It looks like five. You really need a divider or dummy board in there somewhere. I would have the nuc frames against the back wall and expand towards the entrance wkth just a couple of undrawn frames at the most.
Not sure what the queen excluder is doing there. If you must store it with the hive, put it above the crowboard until needed.
Does the hive have an OMF? If so close it up for a short while.
The important thing is to retain colony (particularly brood nest) warmth, so they can expand the number of brood. More bees means more construction workers for wax building and more house bees to service the enlarging brood nest.
Regards, RAB