Hello Marry,
Nutritional needs result in a uniform stress in the leaves like dark veins or a leaf showing solid discoloration. Yours looks to be infestation. Pests feast on the undersides of the leaves and break the cells. These liquids attract pollen, mold, and new insects or spores. Use a strong spray or shower to fully saturate all parts of the leaves. If the soil is saturated, allow to dry outdoors. Repeat process at least weekly over a one month period. Remember that more is not always better. Soil saturation breeds disease.

Ed