Swarm or something else?

[Waveeater]

On Sunday morning around 10:30am I noticed a lot of action around one of my hives, which is made up of five 8 frame mediums. Under the SBB was a ball of bees about the size of a basketball. I have seen bees on the bottom of the SBB before but not this many. I assumed it was a swarm that had not taken flight so I captured them. I did not see the queen but didn't look very long. I did put in a frame of very young larve just in case. Now today I seen the same thing happening to another hive. Another large group of bees under the SBB. It's got me wondering if they are swarms or something else. By the way I made walk away splits from these 2 hives on March 21st and do not know if I left the queen or if she went with the split. Any thoughts? Tried to attach photos but file was to large.

[GSF]

Maybe forgers returning and being confused with the scent in multiple locations?

[Acebird]

Don't know.  Was the hive in swarm mode before you split?