spraying plants

Is spray n grow any good anyone every try it ? or is flowers kiss better ? Spray-N-Grow

Ihave powdery mildew starting on a couple of plants. I have treated them earlier with Potassium Bicarbonate. Worked good but 3 weeks later came back. Since then I have increased ventilation and treated again by brushing the leaves with it. ( Too much work). My question is..... will it hurt me...