Have you sprayed anything on your plants? How is air flow and humidity? How long ago did it start and where on your plant and leaves? Bottom going up and edge of leaf and moving in, or the whole plant and leaf at once? What is the PH of your soil and feed water, and what nutes are you using and how much? What is the age of that plant? Is this the only plant that looks like this? What kind of lighting and the distance to your plant? This info would be helpful.