Kitchener, ON: 4 Black Orbs w/ Orange Lights; Hovering, Interacting, Moving as a unit, no sound, flew straight up

At approximately 9:20 PM, two unusual orange lighted-orbs were spotted from a southeast facing fourth floor balcony on Heritage Street in Kitchener, Ontario. The objects were moving northward, directly towards my building from the south-southeast, one slightly in front of the other, very close to each other.  The orbs slowed, and began hovering slowly towards each other, almost so close that their lights touched. It was at this time that two other orbs, the same shape, size and colour, were spotted heading towards the two original orbs.  The first two orbs turned off their orange lights, and it was at this time my partner and I clearly saw their spherical shape and black colouring. All four orbs hovered together in a unit, moving at times slightly closer to one another, but staying in the same general area.  My partner and I guessed the orbs to be no more than 3-400 metres above us, and maybe 1k away.  The newer arrivals also then turned off their lights after a! few moments. (At least, it looked like the lights turned off - perhaps the light was swallowed by the cloud coverage?).  After a few more moments, the orbs, as a unit, flew straight up into the clouds and disappeared from view.  At no time did we hear them making any noise, and no matter how they moved, we did not see any other shape other than a sphere (no side profile of a helicopter or other plane-like shape).  
A report of the event was phoned in to the Waterloo Regional Airport (located very close to the four orbs) but the response was that the airport had not noticed anything unusual. 
Drones? Advanced technology test flights?