Hello! I have an outdoor flathead hydrangea in a pot that is at least 15 years old. It has always bloomed well, but this year it seems to be dying. The blooms from the top downward are becoming brown, and each bloom is covered with a fine web. The leaves are also turning brown. This happened very fast, in about a week. The blooms towards the bottom of the plant are still blue, but I think they will succumb as well. I've attached some photos. Is there anything I can do to save this plant? thanks very much for any advice.