Thank you for your question, Amy.  Have you had your soil tested for pH and nutrients?  How often are you watering the plants?  Are you using a soil water meter to see if there is an adequate amount getting to the root level?  Many symptoms as you are observing are inadequate water and/or nutrient deficiencies, not diseases.  I suggest that you get a soil test, and follow their recommendations.  This Sherwood lab is the closest:  https://al-labs-west.com/

Good luck!