I'm growing plumerias for the first time and planted 3 trees but all of them got rust on their older leaves, they definitely came from the nursery already sick and since I noticed and discovered what it was I started spraying them with fungicide (bordeaux mixture) it seems to help, one plant also came with black tip and this fixed it, my question is the affected older leaves still have the yellow rust spots so I'm unsure if I should remove them, cut them off or let them fall off naturally since it will be winter soon, the reason why I'm unsure is because this plants are new, young, about a meter high and only have a few leaves, will they survive if I take all the old sick leaves and leave them with the new small leaves only? They each have about 5 or 6 small baby leaves and about 4 or 5 large older leaves that are sick. Besides the rust the plants are very healthy and adapting well.