I was referring to the connectors on the esc rather than the connectors on the batteries. It does sound like it was the esc that hurt the packs and not viseversa. If you don't have a dvm to test it with then here's one more way to test it , but it does require a battery that is fair.

Plug one pack into the connector. If it's ok , then unplug it and plug it into the other connector. If one of them shorts then switch either the blacks OR the reds.