Our leghorn is 6 months old and has been laying for about 7 weeks now, consistently and well. However, in the last few days/nights, she hasn't been leaving the nest box. She sits in there all the time and makes a fuss when we try to encourage her out of the box. We only have 4 chickens and therefore only one nest box. Is this normal behaviour? She was previously out and about with the others and active in the run, and she seems to still be interested in food but she spends most of the day in the box now, while the others are in the run. The poop seems ok, colour and consistency is normal. We checked her physically, the crop is ok and she doesn't appear to have any wounds or physical problems, clear eyes etc. What could be wrong? Is her sudden need to just sit in the box all day/night something to be concerned about? Leghorns aren't normally broody types.