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They are obviously not roosting yet. I've had some that started roosting at 5 weeks and some that took over 12. Many people report their chickens took much longer to start roosting. I don't know why there is such a difference, but there is. It is not anything you are doing. Until they roost, they tend to huddle together in a fairly low place they feel is protected. You may be able to clearly see it is not the safest place for them to spend the night, but they think it is.
I'd suggest a few possibilities. You can lock them in the coop for a few days if you have room in there. Let them get used to it as home. Don't let them into the run at all. Chickens are creatures of habit. If they get in the habit of sleeping in the coop, they may start going to bed on their own in there.
Another option is to physically put them inside the coop every night and close the door so they cannot get back out. They should get the message. I've had to do that and some pick up on it after one or two times. Some can take weeks. If possible, set them on the roosts so they get in the habit of sleeping up there. For this to work, it probably needs to be dark enough they can't see to come down. At 14 weeks, if you can get one or two used to sleeping on the roosts so they go there on their own at bedtime, the rest will probably soon follow.
I don't know what your physical set-up looks like. When they do decide to roost, they will look for the highest place they can find. That might be some place in the run instead of in the coop. I do think you are better off training themn to roost where you want them to instead of totally leaving it up to them. It is usually a lot easier to get them in a good habit to start with rather than trying to break a bad habit.
Good luck, and once again,