I noticed some PM slight on my outdoor girls yesterday, lower leaves is where it usually starts, sure enough some nearby bushes have it like out of control. I dealt with it this spring indoor as well by pulling air in to cool from outside, was filtered but not enough I guess
The best I've found for controlling it and keeping it at bay is the following solution. It stops the PM by raising the PH on the surface of the leaves/stalks/budding areas to a level where it can't grow. idk that it removes/kills it but it definitely stops it from growing on your plants. Try it, apply weekly until harvest. Doesn't hurt the plants at all.
2L of water, 1/2 tspn baking soda, 1/8 tspn dish soap, 1/4 tspn vegetable or olive oil. Mix well, pre-mix it a couple of days before you're going to spray it as it mixes/dissolves better. If you're using imperial measurements, double up the ingredients to 1 US Gallon.
If you're in an area which has PM outdoor and you're growing indoor, do whatever you can to avoid brining in air from outside or put a good filter system up. It's a bugger and I've found that my neighbourhood has PM all over the outdoor plants %$^! imo it does not develop indoor, it's brought in from outside, then you have to clean the shit out of everything to kill it before growing again. It's worked for me indoor, haven't seen it after I cleaned up the room with bleach between runs and eliminated bringing air in from outside. Good luck.