Their birdbrains are not wired for logic quite like ours. Sometimes it is really hard to figure out what causes their behavior.
The way I understand it they were all roosting inside, then about the time we switched back to standard time one or two started roosting outside while one or two roosted inside. Over time they all moved outside to roost. The light was installed after some started roosting outside to try to draw them back inside. So putting the light in there is not the cause.
Aart has asked some really good questions. They are creatures of habit so something happened to cause them to move outside. The time switch seems suspicious but they do not wear watches or understand how to read a calendar. If that had anything to do with it, it was because you did something different or something else changed, maybe a security light on a timer? The days getting shorter would not cause that kind of change, they go to bed by the sun, not a watch. So did you do anything different according to the sun, like feeding then treats in the run too close to bedtime?
How much roost space do they have inside? Are they crowded? That could have something to do with it.
Sort of in line with the crowded roost question, my chickens are most brutal toward each other as they are settling down on the roosts getting ready for bed. Where they sleep depends on the pecking order and where the top ranking chicken wants to sleep. They can be pretty mean moving others out of their way.
Sometimes one chicken will go out of their way to beat up others lower in the pecking order, actually moving from their standard roosting place to go beat up others. I’ve seen this happen regularly when I’m integrating younger chicks. The ones getting beat up look for a safer place to roost. This behavior normally does not happen when the pecking order is settled and if they are all the same age, but even with my adults the ones higher in the pecking order sleep on one end of the roosts near the window while the lower ranking ones are at a the far end. By seven months yours should have all this worked out, but maybe one is late maturing and the pecking order is shaken up a bit as they resort. With the roost outside maybe they have enough room to sleep together without being too close.
I’d suggest checking your coop for roost mites. These only come out at night, hiding in the coop during the day so check after dark. They will run from the light so do it in the dark with a flashlight and look in the vent area. You can see them running away from the light.
It’s possible something frightened them inside the coop. It may have been some critter, maybe some change you made, or about anything. They frighten pretty easily.
So what can you do other than take down that roost in the run? If you have room you can try adding a bit more roost space, but that’s probably not the problem at that age in spite of all I wrote above. Check for mites. After dark, toss them inside the coop and lock them in there until they start going to bed on their own. They can be retrained.
Good luck with it.