Why are my white sheets getting thin 3" long stains from the dryer?

Why are my white sheets getting thin 3" long stains from the dryer?

I hope you can help. When wet, white and light colored clothes go in to my dryer, they come out dry with random skinny 3" long rust-colored stains on them. My guess is that ALL my clothes are being stained but I only notice on the light colored clothes and light sheets.

ANSWERS: