Why such soft shells?

[Trishkabob]

Our eggshells seem to be getting softer. our 5 girls are 5 and 2+, have charmed chicken lives (every day they are out and about on our property, in addition to their layer pellets and calcium in a bowl in their pen. No fertilizer/ chemicals in our grass or anything).
Could it be age? It isn't a huge deal, no shelless eggs, but just doesn't have that satisfying crack on the bowl or spoon. maybe the older 2 are into their dowager stage and even though they still lay like champs they just can't make those hard shells.
But the 2 yr. olds?

 

[Peep-Chicken]

Do you feed them oyster shell at all?

 

[sunflour]

The older gals can have thinner shelled eggs, but the 2 yo gals should not.

Assuming there are no signs of illness at all, then make sure they are actually eating the Calcium supplement, top their feed with it.

If you are sure they are eating oyster shells, the it could be a Vitamin D3 deficiency and you could try supplementing it.