Marius,

Rust looks like leaves are sprinkled with very coarse ground pepper, but brownish-orange in color, not black.

You have to look closer to see. Also you may have another fungus issue, like anthracnose, perhaps not too serious, more a cosmetic issue.

On your upturned leaf photo, are those little light colored spots here and there under the leaf's surface possibly an insect egg or a leaf gall (insect inside the gall)?

Moses