I have a problem with primarily my clematis. The leaves have started to go brown round the edges. I left if for a while hoping it was nothing, but it has spread all over the plant and the leaves seem to be crumbling. It has spread to my montana which grews next to the said clematis. I do not believe it to be clematis wilt as it now seems to be affecting a shrub which is in close proximity. I think it is some kind of fungus similar to mildew. Any advise?