Thank you for your question, Nancy.  Dogwoods (Cornus sp.) have had a rough year.  They prefer shade, and lots of water, but too much water may deplete the soil of nitrogen, resulting in chlorosis (yellowing).  I don't know your plants' care or environment.  I suggest that you get a soil test for pH and nutrients, and ask the lab for soil amendment recommendations for dogwoods.  This article has a list of labs to do that:  https://catalog.extension.oregonstate.edu/em8677
I hope that they can help.  Good luck!