First year beek here. I know that one of the causes of swarming is overcrowding so I gave my 2 hives double 8 frame deep brood boxes before the supers went on over an excluder; both hives have still swarmed. I had tried splitting the second hive after the first had swarmed but to no avail. I would have thought 2 boxes/16 frames was sufficient space so where did I go wrong? Should I have pulled any frames with stores out of the brood boxes?