to me that screams bugs or fungus. i default to soapy water treatment for either of those two problems.

i'd spray them once every other or every third day with dishsoap mixed in water (like about a tablespoon per cup, or until the water is tinted the colour of your soap). if the problem doesn't get better then try and find something for that specifically. the soapy water can't hurt the plants and it's cheap.

Iris leaf spot. Nothing to be worried about. Just ugly. You can discard leaves like this. If you spray with a fungicide it will only inoculate uninfected parts of the leaves. Bad some years, other years none (without spraying). Rain isn't the factor. Don't believe anyone knows.

May use rose fungicide or Daconil - no reports of one being superior to the other.