A potted everlasting sweet pea in my garden nearly died due to lack of water earlier this year. I managed to revive it but its older leaves are yellowing and have what looks like powdery mildew coating many of them. The upper leaves are largely clear and the plant seems to have begun growing well again. Can anyone confirm that this is in fact powdery mildew? I can rub off parts of the white coating with my thumb which I read may suggest it's not powdery mildew.
If it is indeed powdery mildew then is milk and water the best way to treat it? Should I just remove the leaves that are worst affected?