Noticed a water leak stain in my ceiling in the drywall. Cut a hole and noticed water drops dripping from the joint of a metal round air duct. This duct leads to an external air vent on the side of my house. It is currently extremely humid on the East Coast And I suspect that is somehow related. My plan is to seal the joint with mastic and fiberglass joint tapeIs. Is there anything else that I should do?
PS: In the above photo I have removed one sheet metal screw so there is a visible hole there