I planted 4 new dawn roses a year and a half ago as they are known to be tough and disease resistant. They are in different spots in the front and back gardens with 2 in full sun and 2 in partial shade sun. After growing beautifully all of last spring and summer, all 4 were riddled with rust last fall and so I plucked all the leaves off, did a dormant spray of horticultural oil in February and as they started leafing out, I have sprayed with copper fungicide every week or so. They have been sprayed at least 4-5 times so far this spring. They are putting on beautiful growth but ai have again found the beginnings of rust on all 4 roses 😫 Does anyone have other ideas as to what I should do? They have good air flow, I feed once a month while they are growing with rose tone and I have plucked the infected leaves off. Should I try a systemic fungicide instead or more horticultural oil?