Discreet spots on leaves that occur in a pattern such as along the margins is usually a sign of a nutrient deficiency. That looks similar to either potassium or magnesium deficiency. However its not as simple as just adding more of those elements. The problem could be root stress from not having good enough drainage which prevents oxygen from getting to the roots. It could also be that the pH in the medium is off (this is a very common problem that happens easily).
To determine what is causing the problem, we need to know what medium(soil) you are using, what nutrients, and what water source? Each of these can cause issues with nutrient lockout, or pH lockout.