At what age should my flock start laying?

[chickletteSarge]

We have a mixed age flock.... 3 are almost 7months, a few are 5-6 months and the majority are 4 months. Out of almost 20 in our flock 1/4 are cockrels. Only one so far will mount and try to mate with the older POL hens we have 2 prod reds that he likes to mount. They so far are the only layers. My next Q is how soon will we be getting fertilized eggs?
thanks for any info/input

 

[chickletteSarge]

Oh yea breeds may be helpfull!
We have FS fowl and only 2 banty breeds.... they are in order of age oldest to youngest:
production reds (2)
necked neck (1)
houdan(1)
barred rock(2)
sumatra(1m/1f)
silkie pr
D'uccle pr
yolahama pr
Sex link (1)
cochin pr
wyandottie(1)
i think thats it?
From the silkies on they are the 4 month olds if anyone has breeding and laying info in theese breeds id greatly appreciate it!
thanks again in advance!