coven army question

so I'm making different coven lists and i was wondering about freakish spectacle- “Enemy units within 12" of one or more models from this Detachment suffer a -1 penalty to their Leadership value.”

multiple formations in the covens codex get this as part of their special rules but it dosnt say if the different formations spectacles stack or not if within range... basically i want to watch my opponent get frustrated when he gets alpha'd an his army routes before the game has a chance to begin.

I would say yes.
There are rules out there that specifically say "Within range of a model with this rule", but this one clearly says "models in this detachment", so with multiple detachments they would in effect count their Spectacles as being completely different. One is horn-rimmed, one is veri-focals, but both are freakish, and thus stacking of the leadership modifier.