My hens are about 3 years old, none of them have been laying very well for probably the last 6 months, I thought it was just from the winter, but egg production has not improved and it's nearly June. I have also had 4 girls mysteriously die since December. They are fine when I check on them at night, and dead in the morning. No signs of injury or struggle, no messed up or missing feathers. They seems to be eating the same amount of food as always, stool seems the same as well. They free range when the weather is nice, they are fed layer pellets from the feed store, oyster shell free choice, and grit when I can find it. Nobody seems to carry it around here and when I ask them for it they look at me like I'm stupid and say "that's what the oyster shell is for"...but my understanding is that the oyster shell gets digested and not stay in their bodies very long. Is this wrong? Could they be starving to death because they can't get the nutrition from their food? They're too young for it to be an old age thing aren't they?