when i get a plant like that i cut all the leaves off and water/fertilize. i figure that if the roots are deficient, that will take the load off them, since there will be no transpiration from the leaves. if it's indeed rust, that's less food for it.
i never worry about knocking the leaves off my ailing figs, since figs have no problems regenerating them once the problem is alleviated.
this is what i've decided to do with my ailing black madiera. cut the leaves off and put it in full sun, fertilize heavily, and whatever happens, happens.
of course, we've all got our own style :).