I was recently surprised to hear one of my Salmon Faverolles singing what I was sure was an egg song. I bought two pullets as chicks in May, but as far as I knew, neither was laying yet. My June chicks last year didn't lay until this spring, so I wasn't expecting anything.
Then, a day later, I discovered Celeste hunkered down in some foliage behind her coop. She had found a nesting area that the runner ducks sometimes use, and Celeste deposited her lovely tan pullet egg next to a large, white duck egg. In fact, since the ducks were winding down for the year, I hadn't checked for duck eggs for a couple of days, and Celeste had actually laid two eggs there. So, I really did hear a proud egg song the day before!
Now, both she and sister Camille are laying an egg a day. One likes to lay anywhere in their coop, the other favors a nest box in someone else's coop -- once the geese have moved to their tractor for the day. One lays in the morning; the other lays mid-afternoon. Chickens don't really care for humans' ideas of when or where to lay eggs.
Although all my other girls seem to be done for the winter, I do use fake eggs in everyone's coops. It might entice them to lay eggs where I want to gather eggs, but I mostly do it to discourage anyone from breaking and eating eggs, which was a problem with my first set of hens.
Your girls will likely come around in their own good time.