Black streaks on Rear After rain

Hi, the black streaks that you mention, do you mean the dirt spots on the top of your bumper on the picture? If yes, that's normal. The rear of a CT gets dirty very fast when driving in the rain. It's just caused by the design of this car. Some people fitted mudflaps and it supposed to get less dirty but I can't tell for sure since I haven't fitted those.

The part that's missing is this I think:
Cushion - Lexus (75129-AC010)

Good luck!

When I was little I always thought it never rained in Hawaii...)
But I think there is nothing you can do to prevent this other than not driving in the rain, wrap the rearbumper in black or trade it for a black/dark car... Well, the streaks will still be there ofcourse, but at least less visible..😊