Looks like wetness above the lower joint. If the pipe were draining properly, there would never be a puddle like that at the top of the lower joint. The cast iron should be a couple of inches into the lower coupling, and water does not flow uphill.
The top joint should be make with a banded couple to keep the joint aligned. The coupling you have there is approved for use below grade, not inside a wall.
I would go back and be sure I knew exactly where that liquid came from.