Stop Powdery mildew

Anyone have any suggestions to stop powdery mildew. I have sprayed with potassium bicarbonate and after a few days the mildew comes back. The humidity is 40-60% in the room. I have sprayed 3 times. Thanks

I read a couple of other posts on powdery mildew using ammonia. I’m gonna give it a try, but if anyone has another suggestion, let me know.

@tasl milk or lactobacillus treatment.