I have 5 free ranging hens. Ever since they were transitioned into the coop as young pullets, they have always went into the coop at dusk. The past couple of weeks, one chicken has been staying out later than the others. I usually go outside to close them in at around an hour or so after dark. Whenever I go out there, this chicken is still walking around. The past few days when I went outside, 4 of the 5 were still outside. Last night I decided to let them stay out as long as they wanted, just to see if they eventually started to walk back towards the coop. About 5 or 6 hours after dark, I went outside and the 4 were at the far end of the yard, away from the coop. Only one chicken has been consistently going inside at normal time. I have never had this problem before. Any advice on a way to fix this and why this is happening is greatly appreciated.