its hard to see from those pics, but take a look under your leafs for any flys bugs they usually look like whit dots or black dots. but also you could be getting some nute lock , usually caused buy over watering. when you water are you letting the soil dry out? usually the soil test is use on finger to dig a small 1/2 to 1 inch hole and if it is wet in their let it dry. top soil can be dry but 1/2 inch under can be wet. keeping your roots constantly wet like this deprives them of air. just something to look at.