If they are activators, why are you using PlaceAtMe?
Wouldn't it be better to use Enable and Disable?
Place all three activators, and set the other two as 'initially disabled'.
The master activator then links to the other two activators as ObjectReferences.
You then can enable or disable the other two activators when-ever you want, based on your conditions in the master activator. You did not say much about what you are doing with them.
It's an farming mod, the first activator is an mound of fertile soil created by the player, normal plants is just one object controlled by the soil, however crimson nirnroot is two activators, the grown plant and the harvested plant.
Then the grown plant is activated/ harvested it give you an nirnroot, enables the harvested plant object and disables it's self, the harvested plant start an countdown and enables the grown plant and disables its self then its time to regrow.
My first try was to create the harvested plant and delete the grown on harvest and to the opposite then regrown, dirty and no way to access the soil interface and delete the plant.
I could just use enable and disable, then the soil would know both referances and can delete them, however then the plants need to know each other as I has no way of telling grownnirnrootref about harvestednirnrootref and opposite.