In front of my house I have 4 roses (I don't know what type they are) and they have been there for 5+ years. But in the last month the smallest one got a black dot on a leaf and after a couple days all the plants had it on almost all of their leaves. Is there anything I can do to save them from this? I heard that watering from the bottom and not getting the leaves wet would help with not spreading it. The dots are only on the top of the leaves and they turn yellow and fall off after a day or two.