Probably drone brood that didn’t make it out would be my guess for those 4 cells, as for the brown spot, it might just be the color of the wax.I dont think it got chilled? I had capped swarm cells last week and did an unplanned split. This frame is from one of the newly split hives, 7 days after the split. I am pretty sure there were a lot of bees in there. It did get a little chilly (50’s) for 2 days but I am thinking there were enough bees to cover them. I could be wrong. After closing everything up I realized it would have made sense to open those 4 drones and see how they look. The spots definitley don‘t move.