I have a Staghorn that has developed a Brown growth on the bottom of the lower leaves which I think is rust and on the upper leaves there is a silvery growth over the underside of the leaves is this natural or is it the start of rust? Can anyone tell me how to treat for this problem? I think it is also affecting my Orchid plants that are in the same area should I treat these at the same time and with the same product or something else. Help needed urgently!!!!