Hi again,

Firstly, and I should have said this in my previous post, your plant looks very healthy overall. Treatment of any kind may not be necessary. If it seems like the condition progresses to a worse state, then it should be considered.

Secondly, assuming this is a leaf spot fungus, cinnamon will not work. You need a systemic fungicide, not a strictly contact fungicide, for leaf spot diseases. Cinnamon is only a contact fungicide. (For the same reason, sulfur also will not work on leaf spot diseases.)

Thirdly, not all "chemicals" are harsh. The fungicide I use is a clear, odorless liquid with no corrosive qualities. (Unlike many soaps & cleansers.) Many people seem to consider any manmade product to be evil. I won't go as far as to say it's a hysterical reaction, but it is an overreaction. Don't get me wrong, I'm all for reducing the use of any product. Prevention, by practicing good plant hygiene (including isolating new plants), is the best way to avoid problems. I guess I am saying, however, to not necessarily fear a product if your first lines of defence against pests (insect, disease or whatever) let you down. Good luck!