I'm a new beekeeper and got a nuc in mid-June. The bees had pretty much filled the first box and I added another in the beginning of August.
Nuc has been quite long and there should be more bees than what you tell. But if it get a lot of honey, combs are few.
Now you should extract capped frames so you get more space for brood. If she does not lay more, may be that queen is not a good egg layer.
Small hives have problems if they get too much honey.