From what I can tell from that picture it looks like your plant is under attack from a bug. Check the underside of your leaves for anything moving. Use a loupe, not just your bare eyes.
Otherwise I can only assume the soil you are in is too rich in nutrients.
But you have to give more information. What soil are you using? What nutrients are you using? How often are you using nutrients? What is the environment like around that plant? The more information you can provide the more help this community can be.