I have several red alder in my suburban backyard. All have been very healthy and gushing forth bright green leaves all spring. Suddenly in the last few weeks they have all begun to show yellow leaves that are now dropping from the tree. Interestingly, all the other leaves on the trees, at least so far, continue to look very healthy and green. We have had a very mild spring in west Portland, with intermittent sun and grey and rain. Seemingly not stressful conditions for the garden. Please let me know your thoughts. So grateful for this service, you've proven so helpful to me and my native garden over the years.