I do not believe that the spots are any kind of fungi or mold, but a sign of a nutrient deficiency. Marijuana needs different things during different times of its life. In veg, you want something with a fair amount of N and less P and K. During flowering you need something with little N and more P. You also need micronutrients. Some soils may provide enough nutrients, but in general, not. However, I believe that you have your plants in containers outside and not planted in the ground, don't you Uruguay? If you are using a fertilizer too high in N for flowering, it will actually retard flowering. It is important to know what you are feeding your plants.