Where do they sleep? Overcrowding while roosting causes problems. I see you state that they only are using one roost, and that is because they are friends. And the empty roost gives them space. If you filled that roost with birds, the space is gone, and often times trouble will start.
Do you have full size birds? If you have bantam, then you could get maybe get away with it.
Years ago, I got bit by chicken math, and put in new birds, and for a while it worked... I got hit by a predator, which made me sick, but I noticed something, even though a predator had just been in, my birds were mORE relaxed, the flock was much more peaceful, and they started laying better.
You can try it, but consider, do you want happy healthy friendly chickens laying eggs, or do you want ragged, feather picked, scuffling chickens, cranky and pecking at each other.
Mrs K