are you using plant food? how often do you water? do you have hard water? it looks like minor root damage. i cant see the roots, but when a plant takes some root damage, it has a hard time getting everything where it needs to go, and shows some problems up top. do you have a TDS meter? a TDS can help you determine whether your water is the problem. A good reading is about 75-100 ppm. if you take some clean water, and test it with a TDS, then pour it through the plant, catch the runoff, and test it again, you can see whether the plant has a lot of salt buildup. also, keeping your pH in the right range at every watering is essential. use the same process of pouring water through & testing the difference. use distilled or very low TDS water, because it will not hold its own pH, it will go to the pH of the medium as it runs through. go with 6.2-6.8 for soil plants. One of the first bits of knowledge i ever received about watering is still one of the best. you cant overwater a plant in a single watering, but you can water too often. the weight is a good indicator of when a potted plant needs a soaking.
good luck =D