I looked at the leaf tip under 100x microscope and discovered white hairs on this tip that had turned grey..I'm no expert but considering the humidity levels spiked at night, and looking at powdery mildew pictures online under a microscope, I wasn't gonna take any chances..I took this bitch outta my show and sprayed the remaining crop with baking soda/water mix..lowered humidity levels, increased my poor ventilation with a can filter and multiple fans after removing the bitch with dirty tips, plus chopped some tips off of another questionable spot. Now I'm just praying...any other advice besides better growing conditions? I think the humidity dome/ high r.h. plus poor air circulation started this.. hopefully better air + humidity levels keeps the PM under control...