I have 4 hydrangea plants that have really been thriving all summer. But lately I've noticed that they're starting to get brownish spots around the edge of the leaves, and in the center of some of the leaves. I did some research and I think it could be a fungus. How would I confirm this? And what should I do to treat it?
Also, the new leaf growth is coming in very pale and yellow. I guess it could just be associated with the season changing, but I am assuming this is probably an iron deficiency. Have any suggestions how this could be remedied? Just add iron, or is there something else I can do?