I found one of my Rhode Island Reds in her nesting box at 5pm this evening, but a moment later she got up and I saw that all she'd laid was yolk and egg whites. No shell, no "rubber" egg. Just the insides. This is the first time any of our chickens have laid a less-than-perfect egg. We currently have them on laying feed, they are free-range during the day, and have access to an entire road paved with oyster shells. So they shouldn't be deficient of Vitamin D or Calcium. Any thoughts? I also found it unusual that she would be laying so late in the day. But our chickens aren't really on any laying schedule -- generally all 8 of them are finished by around 2pm.