When you use "ob object touched" it already "picks" that specific object for you. Under the events of this condition, you will exclusively be manipualting this single object, not the whole family.
The difficulty you are facing now is actually very important because it's a door in c2 that when you open, you get +5 levels or so:) It's called "picking", you should definately read about it in forums, in manual and watch youtube videos. Believe me, you will thank me later when you solve the picking with all aspects.