Night time Egg Layer

I know that this has been a topic of discussion on some previous post but thought that it would be good to discuss again. We have a small flock of 5 chickens= 2 phesant rocks, 2 rhode island reds, and 1 white rock..... we had two white rocks but lost one a few weeks ago to a wandering dog in the neighborhood. They are all about 22 weeks old, give or take a week. So far we only have 1 red who has been laying regularly for the last three weeks, I don't know if she started early or if the others are just behind!

Anyway, our one and only layer has been laying regularly.... I think the third day she didn't lay but hasn't missed a day since. The first egg she laid was an afternoon egg, I think it came at about 2 pm. Then she started getting on a regular schedule typically laying by 11 am, however the last few days she has been really off schedule and in fact we have been getting eggs at night. Two days ago she didn't lay on her normal schedule so I thought that perhaps she was going to skip a day. The next morning at 6:30 and before day break we had an egg in the box...... red was not on the roost when I came in so she laid during the night or early in the morning. That was the only egg we had that day.

The next day, the same thing. Go to the coop at 6:30 a.m. to give them some food and there she is sitting in the box on an egg that she laid at night or early in the morning, at least this time she stayed in the box and didn't try to get back on the roost in the dark. Even is she is laying early in the morning she is still doing it in the dark.

Has anyone had any expierence with night layers?? Could this be a result of the other chickens coming into their laying cycles?? Just trying to get a handle on what might be the result of laying at night.... we just don't want them to get into the habit of laying from the roost and having broken eggs. Thoughts, comments, etc. are always welcomed!