Looks lokie classic mold starting to me.

Watch carefully as if it is, you'll prolly lose the plant.

If the leaf begins to turn first light green then yellow AROUND the spot, and grows out into a circle around the dot, its mold.

If thats the case, only remedy would be chemical agents,,,which you may not want to smoke.
HARDDON Reviewed by HARDDON on . Black Spots (Picture attached) I Have Some Black Spots On My Leaves And I Donā??t Know What They Are Or Where There Coming From, Any Ideas? The Plant Looks Good And Is Doing Good..But I have Black Spots. Thanks South. Rating: 5