Garden Pests and Diseases: Black Spots on Basil Leaves, 1 by dividedsky

dividedsky wrote:
I started these seeds indoors with lots of other plants. These are the only ones that are showing this problem. Coco coir with a few pellets of controlled-release fertilizer.

I have no idea what's causing this. Any guesses? Does it look like a disease that will spread to other plants (get rid of the basillings) or some sort of nutrient/environmental issue (stick 'em in the garden and see if they recover)?