Hello. I planted this Lapins Sweet Cherry tree last fall. It was doing fine after winter, and was growing vigorously. However, recently it has developed some reddish spots on some of its older leaves. The disease seems to be spreading from the leaves closest to the trunk. I have attached photos. I suspect it may be a fungal disease. What can I do to treat for the disease other than picking off and disposing the affected leaves? Are there any preventative measures I can apply right now? Thank you!