08 black streaks from Access windows

I just bought a used 08 Tacoma Access cab PreRunner truck - white with tan interior. I love the truck. One issue I'm having now that we're finally getting some rain here in TN is that I get black streaks running down the side of the body under the rear side windows - like the rubber gasket around the windows is starting to disintegrate. Has anybody seen that and is there a fix for that?
thanks for any advice!
Jan

 

As much as it has rained recently, I would think if it was dirt it would all be washed out by now. I'm concerned that the rubber gasket behind the glass (which I can't see from the outside) is breaking down. I wonder if that is normal? Anybody else experience that?

 

My '06 AC did this from day one. The streaks wipe off pretty easy after a wash/rain so I never worried about it.

 

My 08 Prerunner access cab has also done this since new. Like others it washes off easily & I don't worry about it either.

 

Mine does this on the bed sides. I can wipe it off easily, so I really don't care.

 

Mine also does the same ... not worried about it.