Well, the shortest day of the year just passed so a lot of those ladies might start thinking about laying pretty soon.

All are individuals though, regardless of what's allegedly normal for their breed. Some may even sing the egg song when they get startled shortly (weeks) before they lay.
When you notice a lady gone missing and nothing else out of the ordinary... she's probably busy. Sometimes it can take a couple of hours. I've seen broody raised chicks and a (boy)brood mate both be told to stay while the hens went to lay their eggs. I'll never figure out how they communicated it AND got cooperation! But it was sure cool to see.
Egg binding is possible even at the first one, but that probably isn't it this time.

Always good have things on your radar though! Oh and white leghorn are quite striking to see their big red combs on their petite bodies. Everybody just loved to see that girl, she was a character too. Pics of the other end ALWAYS welcome!
Eggs are coming, very exciting!