Very thick, hard egg shells.

[wanmom]

I got new chickens a month ago. They are now 26 weeks old and producing beautiful eggs everyday. My question is...I have had oyster shell available to them all the time and they go through alot of it. I have noticed that the shells are very hard. Is this a problem? The eggs are perfect just wondered if I should back off of the oyster shell?
Look forward to your experienced comments,
Thanks

 

[gdplum]

...hard shells equal healthy chickens...plus good exercise for you when you crack them.