Many of the shrubs and plants in my yard are dying. I have lost two rhodies and two roses. The rose leaves turn yellow and almost immediately the stem is turning black. On the rhodies the leaves curl and the stem/branch is black soon after. This happens in a matter of days. I have been spraying them with a fungicide which seems to help if I get them sprayed in thie. Can I use the fungicide as a preventive on everything? The lable wasn't very clear. It also totally wiped out my neighbors grape vine in a matter of days.