Apparently drone brood takes 3 days longer to hatch, so these might be just the last of the brood. A queen lays drone eggs when the conditions are right, and a few drones are a sign of a healthy hive. If you don't see any hatched drones in the hive, maybe they have had a drone kill, which they will do for instance when it's cold or not enough supplies. But if you notice drones in any of your hives, there will certainly be more around in the bush. It's unlikely you have a laying worker, because she'd be laying a lot more drone brood than what you've got. What are your temperatures at the moment?
Remember that cold climate hives basically hibernate for the winter, so try not to worry about a queen not laying or even a queenless hive. You said there are good numbers of bees, so you probably just need to observe what is happening for a while as you are doing. Try not to disturb them too much during the time period they might be making an emergency queen. I lost a queen once and they basically filled the hive up with pollen, so it's hard to know if they are simply excited about the eggs you added or it's a sign of queenlessness! And can you hear them sounding upset like they do when they have no queen? I am no good at working out the different noises.