3 of 4 Hens laying eggs. what to do?

[arminius]

I bought 4 chicks in April, they were all born April 5th 2016. I purposely got 4 different breeds which I believe are:
- speckled sussex
- gold laced wyandotte
- ameraucana
- isa brown

I've been getting eggs now for past two months, and only have three colors of eggs. How do I know that all the hens are laying? Is it possible one of the hens could not be producing or ever produce? Here is a pic of collection of eggs for three days.

 

[redsoxs]

Are the two lighter brown ones really the same shade? They look different in the photo to me. There are the two greenish ones, the two large brown ones, but the light brown one closest to the bottom of the pic looks different than the one directly opposite of it. Might just be my pic on my computer but it looks like eggs from 4 different birds are represented in that pic.

 

[arminius]

yeah, it's just the pic.