The leaves of my kaffir lime plant have the grainy discoloration which looks like a disease. I assume normal leaves would be plain dark green. I didn't see insects or aphids living or staying in the plant, just this discoloration. It receives direct sunlight around 10 am to 3 PM daily.
Can you help identify what caused this discoloration? Could it be caused by a fungus? What should I do to make it produce a healthy green color?