Congrats!!! Sounds like the broody flu hit your coops hard! We currently have 3, one is on eggs (day 10) and the other 2 are waiting for eggs from a breeder, hopefully he will get some collected in the next few days... weather has complicated his egg collection.
About a monty ago I had 22 broodies at once. I always have broodies all times of the yr. Not often when I have not a single broody. Its very contagious in my flock.