Prefab Rotation is not being applied

Hello there,

I created 20 levels so far. All are duplicates of 1 level, then I edit each.

I decided to change the Light Direction rotation, so I did it for one and clicked apply (i have it as a prefab).
The prefab has changed, but the rotation in the other levels haven’t changed. If i click on another leve’s Direction Light, and click Select (prefab), it will select the prefab with the correct rotation, why isn’t it being applied to all instances of my prefab?

Many thanks