I have noticed recently I keep seeing these black dots on my calamondin leaves I can scrape them off without much difficulty. Are they mold or a bug of some sort. Also the green stems of the calamondin seem to be a bit more brown in places I don't know if it is these things spreading I scraped them off and sprayed the leaves with hose to try drown and other pests I csnt see. Ive moved it away from other plants.
The first thing that comes to mind Ben is this is honeydew created by aphids and many of the mussel and mealy bug family.
They all excrete a sweet liquid on which rapidly grows a black fungus.
Check the higher parts of your plant and also if your plant is outdoors check the plants above it.