Out of the twenty something plants I have only one has rust!! Not bad!

What causes rust and why do only certain ones get it?? Which ones are typically susceptible to rust??

Sorry but that is not rust. I will try and find a picture and post it.

Courtesy of the internet..... the second picture shows front and back of an affected leaf. The rust displays as pustules on the back of the leaf, these pustules will dry up eventually and turn a grey color but this is usually after the leaf has fallen off.
The scientific name is Coleosporium plumeriae

EEEW!!

Thanks, Hetty. I am the one who asked for pictures. I don't have any plant leaves with this and never have as far as I know. At least now I know what to look for.

rust