I have some Geranium Biokovo and Biokovo Karmina. This is their second season in my garden and they are growing nicely to a good size and lots of lots of flowers just starting to bloom now.

However, I do see that a fair number of the leaves turn yellow and sometimes orange and reddish, especially in the interior of the plant and close to the ground. These leaves as well as some of the green ones also have some little black spots that looks like a fungus of some sort.

What is the cause, and what can I do to treat this? For now I have been removing the leaf and sometimes the stem as well of the discolored and the more fungus-covered parts, but I was wondering if I could do more. When I see 100+ leaves per plant it's kind of tough to pick through and find every one with black spots.

Thanks.