in my outdoor garden (i have other stuff besides Cann) if its brown it might be coffegrounds that stuck in the leaves, soil that jumped with watering, mold or birds with desynteria are shiting your plants (shit happens you know ;p)... i think is mold i would spray it with two mashed garlics for 0,5l of water twice a day till it disappears.. thats my humble opinion as a begginer (I thought that as a begginer it would be bold to answer a thread). if not I would try fluconazol or ketokonazol.