What is happening with our garden
This looks like heat stress to me. How much water is your garden getting? Do you have mulch with compost or ground bark? Have you looked on the underside of the leaves to see if there are any insects? Many plant diseases area host specific. For example, a disease on tomato isn't the same thing that affects a rose or a lawn. There are different problems that require different management strategies. Two common problems on tomatoes are Septoria leaf spot and early blight. You can learn about these, the symptoms to look for, and management options, provided at the following links:
Other common problems of vegetable plants can be found here. https://extension.umd.edu/hgic/learn/diagnose-vegetable-problems
In roses, black spot is a common disease that causes leaf spots. Read this information and see if the symptoms match the problems with your rose.
Fungicides do not cure leaf spot symptoms. They have to be applied preventatively (before symptoms appear) in order to be effective. With photos of the problems, we can help diagnose the problems and make recommendations for you.
I hope this helps. Let me know if you need further information. Thanks for your question.