There was just a M7.3 in Fiji region so despite the near Cuba quake not being a 6, there have been four M6+ quakes scattered around the globe, again, in a bit more than 25 hours. You expect between one every two or 3 days (see thread below), and some amount of those would be aftershocks of larger quakes in same area, so independent M6s might be more line one every 3 days.

Chris