Then there is possibly something about the new location that is causing this. Perhaps a draught from a window or vent, or the view from a window is causing them to perch where they can see out of get more light. You have to look at it from a chicken's perspective, especially of they are confined to the coop all day which can be pretty boring for them. Can you perhaps construct them a predator proof run, so that you can let them out a bit more.
There will be something about that nest box which makes it better than the others even if your human eyes don't detect it and of course, once one bird lays an egg in a nest, it is immediately more attractive to the others. It is very common for all bird to want to lay in the same nest, so I can assure you that yours are not unusual, but making other nests more attractive can change that pattern a little or move it to another nest.