chickens not going in coop after dark

[teachermom24]

We have 18 healthy layers (6 months old) and one banty rooster. Up until last night they would all be in the coop at dark and we would put down the door for the night. Last night we went out well after dark to put down the door and most of the chickens were still in the yard (fenced in chicken yard). Tonight same thing. We checked inside the coop and everything is normal. What's going on?

Thanks!

 

[Beaker Duck]

There could have been something that scared them in the coop, and now they are afraid to go in. ( It could have been something as innocent as a leaf- chickens are funny)
We have had chickens that are afraid to go into a dark coop, and this time of year, it gets dark faster, so they don't always have time to get back to the coop before darkness sets in.
We had a little press on closet light that we installed on the wall. We went outside just as it is getting dark, and turn the light on for them. We only had to do it for a few days untill they got used to coming back to the coop before it got too dark for them.