Re: Laying worker?
That brood pattern is too solid for laying workers. Solid brood patterns like that can be confusing, as the domes can appear somewhat flat. Best way to assure if that is drone or worker brood is to scratch a few caps open and examine the pupa. You likely have a drone laying queen. Possible that they tried to replace the queen after the Formic treatment and she didn't mate. If you can't find her, try shaking all the bees thru an excluder. You'll need to eliminate her.
At that point, you can correct the problem as you see fit, with a frame of brood with eggs from which they'll pull a queen cell, adding a grafted queen cell, adding a purchased queen, or combining with another hive.
Ps. There is never "a" laying worker. When a hive goes laying worker, most of the bees in the hive are laying workers.
Hindsight is 20/10, not 20/20...
After the fact, I always know what didn't work.