Can you lower your headliner a bit to take a look in there and see what'* going on?
You will have to remove the holy sh*t handles to get a look.
I had a big problem, similar to yours, and it was due to unplugged rear sunroof drain tubes.
The water leaked into my headliner, then rode down the door channel and collected on the rear floor pans.
I wondered why my headliner had what appeared to be salt stains. Now I know!
Yours, being aftermarket, could be routed a bit different, but no doubt the idea is the same.
Here are some pics I took during my fiasco: