The queen is laying a tight pattern and the 4-5 middle frames are relatively full. Saw eggs today and her majesty about a week ago. There is a lot of consistent activity in and out of the hive and I would describe it as a medium size hive population.
I'm not sure how to interrept that. I sounds as if you only have brood in 4th and 5th frames, if so what is the status of the other frames? Filled with nectar/pollen?
If you only have 2 brood frames in the hive you're pretty much at a standstill on development as the emerging bees and the dying bees are happening at pretty much the same rate.
Bees will only draw comb under their feet so as the population expands they drawn more comb. As the population decreases the drawn comb is often filled and capped as stores do not require attendance or maintenence like building comb or brood does.
I kind of sounds like your hive is honey bound. Take the 2 undrawn frames and put them between the brood frames so the bees have to cluster on them and the brood. The bees will then draw comb on those frames as they are under foot. Drawing the combs will give the queen more room to lay egss. The population and the hive should then start to increase in 3 weeks after that as the more bees from the larger brood nest forces the bees off the drawn comb and onto empty frames. They will then start drawing those frames.