Am I missing anything? Help me fix my leaky AC duct

I noticed my daughter's bathroom vanity cabinet has a musty smell. I figured it was a leak from one of the water lines. After I inspected everything, I couldn't find a leak at all, but the humidity was 85% under the cabinet and nowhere else. I used a moisture meter and didn't find anything excessive under the cabinet (3-5%).

So I then used the moisture meter on her bathroom walls and found about a 2-foot area above the vanity, right before the ceiling, that was reading 20%. I knew her AC ducts ran right above that spot so I crawled into the attic space above her room, which was a pain in the butt. Her room is the bonus room above the garage so there isn't much space to work with, but I managed.

When I got to the spot that had the moisture issue, I saw there were 2 flexible AC ducts that ran right across that spot. I put my hand between the ducts and there was water/condensation on the ducts themselves just at that spot and nowhere else. The insulation was wet underneath that spot also.

It was raining so I was able to make sure there wasn't a roof leak at all, and there is no signs of water damage anywhere so I ruled that out. Unfortunately, it was hot as balls up there and her AC wasn't on at the time so I couldn't really check for any small holes in one of the flex ducts, but I assume that's what I'm dealing with.

Is there anything else that would cause water/condensation to form between those flex ducts and drip underneath to the insulation? The ducts themselves were completely covered with insulation also, if that helps. If no other cause, here's my plan.

I plan to go up there this evening and fix the issue. I would:
1. Turn her AC on to help find any hole(s).
2. Use straps or string to hang the flexible ducts higher for better access while I fix them.
3. Bring a towel up with me to dry off any condensation on the flex ducts.
4. Use AC duct tape or metallic tape to wrap the ducts where there are potential hole(s). Is there a specific tape you would recommend?
5. Remove any wet insulation.
6. Run a fan to dry out the area for a couple days.
7. Replace insulation once the area is dry.
8. Should I put the ducts back where they were or keep them elevated?
9. I can't think of any other reason that the flex duct would have condensation/water unless there was a rip or hole. Am I missing something? This isn't by a vent register... it's in the middle of the run.

My hope is I can take care of this without having to have an AC guy come in and quote me an arm and a leg. And if he's a big boy, he really isn't getting into that spot.


Thanks for any help and suggestions.