Out of six nesting boxes girls only use three of them, why?

Yes, very common (and normal). We have 6 hens, 3 nesting boxes and they only use 2.

 

Keep them bedded, because one day someone may decide to change locations, who knows why. I've got six boxes for thirty hens, and they mostly only use two of them. Sometimes they change spots, though. Just let it be, and don't overthink it. They are chickens! Mary

 

X 2 - we have 6 boxes and on most days eggs will be left in 4 of them, but which 4 can change from one day to the next. There is nothing to be lost by bedding the unpopular nests as you never know when they'll get a bug in their bustle to use one of them.

 

Hi we have two nesting boxes for three hens but they always used the same one. It seemed to cause problems when they all wanted to lay at the same time. I found an egg in the run because one of our chickens couldn't get into the preferred nesting box. The solution: I bought rubber eggs and put them into the nesting box which wasn't used. The next day we had an egg in each box! Worked a treat we now get eggs in both boxes and no more in the run.

 

Welcome to the world of chickens. Like Mary said don't over think it.

In my 40+ years of raising chickens I've come to the conclusion that they think its "safer" to lay where others have laid or to get in the box with another hen because she knows something I don't about that box.