There is a chance that each hen is laying, but only about 1 egg every 3 days.i feel silly asking this but we have 21 girls and 8 eggs daily. Many of our girls have retired. I want more eggs. How do we tell which hens are laying and which ones are not?
But you can tell who is laying by examining their vent (the hole where eggs and poop come out.)
If the hen is not laying, the vent will look fairly small and dry, and be puckered up. If you have a rooster, check him for a perfect example of a chicken who is not laying. A hen's vent will look like that if she is not laying.
If the hen is laying, her vent will look quite a bit wider, and sort of moist, and look like it is able to stretch enough for an egg to come out.
If I am not sure about a particular chicken, I just look at some more, then check her again. That usually makes it obvious to me.
If you have two chicken pens, or can divide your pen, you can separate them into ones you think are laying, and ones you think are not. Then wait a few days to see if you are right (any eggs from the "not laying" pen will mean you have a layer in there.)
I do not know where you are in the world, but hens usually stop laying for a while in the fall or winter, to molt and grow new feathers. Then they start up again in the spring (unless they are so old they never start laying again.) So you might consider what season it is, when you decide which hens to keep or not.