It would be easier if you make it a BP.
You need a central BP to figure out if the puzzle is solved. You can’t do it with the pillars alone…
Or, you can just make a central BP the player can’t see to do the calculation, but then you have to tell it what’s happening with the cube 
( what is on each face etc ).
So the interface only has this
and the center pillar has
The outer pillars have to figure out if they have been rotated correctly, and then call the interface
