You seem to have lots of disease problems with your plants. You would really be better off to find some local gardeners to talk to for help. You are half a world away from most of us, writing about unfamiliar plants and unfamiliar climate.
In general the yellowing like that is a nutrient issue. It can be from over-watering, which makes it difficult for the plants to get nutrients or from nutrient deficiencies in the soil. The brown spots most likely are another one of those fungal diseases. It really doesn't matter which, because the treatment for all of them is exactly the same: Remove all the spotted leaves and destroy, don't let them sit on the ground around the plant. Keep it pruned for air circulation. Give it as much sun and as little water as it can handle. And treat with whatever anti-fungal you like, or use them in rotation. They need to be reapplied after rain or every two weeks if no rain.
Organic anti-fungals for plants include: Neem oil, baking soda solution, cornmeal juice (soak whole ground cornmeal in water at one cup per 5 gallons of water. Strain the solids out and spray), diluted milk, hydrogen peroxide.