Hello, I have a question about my dappled willow shrubs otherwise known as haruko nishiki. they’ve been coming along fine this spring and now suddenly leaves are turning brown. And entire branches are dying and I’m concerned that there is some kind of disease as it is spreading to many of my 20 or so shrubs. They are about three years old and about eight of them have been replaced already due to the same issue after winter. I’m seeking to understand if this is some sort of fungus or disease and if so, how it can be treated and where I can find the product needed to treat. I appreciate any information you can provide. Thank you.