African Violets and Gesneriads: Scarring on leaves, 1 by figgra

figgra wrote:
Some of my AVs develop this weird scarring on leaves from time to time. Looks like pest damage, but the scars only appear on older leaves, while young leaves look perfectly healthy, which makes me doubt that it's a pest problem.

I have read somewhere that this looks like scars from powdery mildew, but these AVs don't have (and never had) powdery mildew.

I just remove the affected leaves, and the plant may remain fine for months after that, but then it starts again...

Any ideas? :)