Doesnt look like rust to me.some of the The rust fungus spores and color will wipe off on paper towel or tissue. Do this to check for rust. Also when looking at rust on a leaf it will look like a 3d object on the leaf surface, not one with the surface. If u have a microscope u could use that as well to identify the rust fungus and its spores.
I dont think that's what that is though.