Actor Iterators are very slow. IMO you should only ever use them for prototyping an idea. Storing references to all the lights in the appropriate class is a much better idea (store them as Weak Pointers just to be safe).
If it’s a light-switch, then just create a TArray of ‘ALight’ actors (or whatever the classname is) and mark it as ‘EditAnywhere’. You will then have direct access to the lights in the switch.