Thank you for your question about your plum trees' problems.  Almost everyone is experiencing one fungal infection or another in their fruit trees this year, on account of the cool, moist spring.  However, it is sometimes difficult to distinguish between a fungal and a bacterial infection.  Is there any way you can pull off two or three leaves and photograph them on a piece of white paper?  The coloration and shape of the spots are significant in making an accurate diagnosis.

Thank you for your trouble.

Thanks for your quick reply. Here are some pictures. The first 2 are of the plum trees that are very bad and the 3rd is the cherry tree that it is spreading to. Thanks again!

Thank you! I will get back to you by this time tomorrow.

Thanks again for the pictures.  It appears that both of your fruit trees have what is called leaf spot, shot hole or blight, a fungus that infects a wide range of fruit trees.  Here is a link to an article that explains where it comes from and some solutions to manage it physically, primarily by raking up and destroying infected leaves in the fall.  Here is a link to another article with chemical applications to manage this fungus.  Note that only the chemicals with the "H" after them are available to home gardeners.

Finally, here is a link to a very thorough article about various diseases of a variety of Northwest fruit trees, and each category has a timeline for application of fungicides.  Note, however, that not all of them may be available to the home orchardist, and that the time has passed for application before the fungus has done its damage on the plants.  Raking up the leaves so the disease does not reinfect your trees, and controlling the weather are the only two non-chemical approaches.

Hope these are helpful.  Good luck!