J, I think you should be getting a response on this so I'll take a shot at it:

I don't have monarda (a few different agastaches and lots of mints which don't have that much mildew problems but no monarda). Nevertheless, the delphiniums and lupins take a BIG mildew hit every Spring.

Zinnias also have mildew problems late - as well as black spot. Snapdragons nearly always have rust just terrible. I've sprayed Daconil for the last few years and the plants have gained very little benefit that I can see. This year I purchased Spectracide Immunox fungicide and haven't even seen any rust on the snaps nor mildew on the zinnias - the black spot was brought under control before it really began working its way up the plants.

Next year, I'll be spraying the delphs and lupins. Right now, they just have to survive being cut back and starting over again. That's worked so-so for years.

Best of luck,
Steve

Here is a link that might be useful: mildew & monarda - GW