My frikkin' GSX is doing the same thing lately. I have trophies from showing it, if only the judges knew...

You're going to have to take off ALL of the interior plastics, dry it out completely, then sit and watch for drops all around the body panels, brake light fasteners, etc.

I found 4 leaks from my factory spoiler and brake lights like this. It's a bitch. But it's the only way I could find the leaks. Turns out removing and installing a spoiler or brake lights breaks a factory gasket. Nothing sillycone can't fix.