Eggs?

I can't tell you how excited I am for these girls to start laying. We now have 10 hens that are four months old and 3 hens that are a bit younger (well one of those three might be a rooster).

I've read that some hens start laying around four months. So where are my eggs! Okay, I am impatient.
I am looking for anyway to kick start the process. We read that they need more daylight and calcium to lay eggs. Now that they are in their chicken tractor they are getting plenty of daylight (about 13 hours per day) and we are going to change their feed over to layer pellet for higher calcium.

Any other tips? I want to help these girls along and start the laying! We have Buff Orpingtons, Easter Eggers and Brown Leghorns. The younger three are Laced Wyandottes.

We are also needing to choose a material for their nests. Any recommendations?