Do my girls need to have their own nest box to lay eggs?

[peatydink]

I have two girls-a buff cochin and a plymouth barred rock. They will be about old enough to lay eggs within the next month or so. They have a large coop and a nest box that they both sleep in at night.
Do I need to build another box so they have their own space?
They eat well and spend most of everyday out of their coop in our lower yard---I know I need to feed them a different diet once they start laying--is that correct?
Someone has suggested that I put a ceramic egg in the nest box.

 

[Illia]

Only two hens are just fine with one nest box. Even three hens can do with one next box. Their diet will need to be changed once they lay, yes, but only such changes are required like less protein and more calcium. (switching to the 16% layer feed, for example)

You don't need a ceramic egg in there.

btw,

 

[ARose4Heaven]

I sometimes find 5 or 6 hens in one nest. You won't need to add a nest. You might also consider covering the nest box at night. Once they start laying, it is not good for them to sleep in the nest because you will get dirty eggs.

 

[KenLamWV]

Put a 2x4 in there for a roost for them. Just make sure the wider side is up so its laying flat. You definately don't want them sleeping in their nest box.