Can I give my hens egg shells as a calcium supplement?

[Heny Penny]

I have been rinsing and baking my old eggshells to kill any bacteria, grinding them, and offering to my girls in a separate feeder from their regular food for a little calcium boost. Since I've started doing this, I've noticed a drop in egg supply and 2 of my chickens have mysteriously dropped dead (one today and one 2 weeks ago). I don't know if the egg supply and dead birds is a result of the egg shells being offered? There could be many other factors that have caused these problems... Does anyone have any feedback about this? Should I stop offering the ground egg shells?

 

[TheJadeChicken]

I give my chickens egg shells all the time from my family making scrambled eggs. No baking the shells or anything. I do crush them up though.