Where each of the swings individually attached to the upper support, like with eye hooks or what not? or were they all on the same pipe/board/thing?

If all were on the same support, then your own force on your swing can cause the others to move too, just slower then your swing, transfer of energy. The support could be moving with your swing too, a hazard to anyones health if it gave way... You should inform the local church...

I love swings:D