Ther is no amazon product or diy product that will save your plant. All you will do is lie to yourself and smoke moldy weed. Fungus penetrates the leaf and creates a mycelium network below the surface. Cleaning the surface does not rid the plant of the infection, even if it looks clean for a day after you spray it.
cornell formula? nope. neem? nope. Milk? no fucking way, lol, just asking for a terrible rotting smell all over your plants and flower. h202? nope. sodium bicarbonate? nope. potassium bicarbonate? nope. you will find all sorts of people claiming these nonsense remedies work. they do not. Nothing out there is effective nor safe for flowers.
Also, spraying this ineffective trash on your plant will only spread the WPM all over -- on to stems and underneath buds.. drip down to more leaves... because none of these sprays actually work.
I'd be wary of anything that says it is effective and can be sprayed on flowers. things that are safe for vegetables ar not necessarily safe for your lungs. eating and smoking something are slightly different dynamics. you digestive system is techinically outside your body (yeah, soundsn weird but lined with epithilial cells, or 'skin'). Lungs are a permeable membrane away from your your blood.
"organic' absolutely does not mean a product is safe to use on flower.
If it is riddled with it, either isolate it, send it outside to finish, or kill it.
iif it's just a few leaves, try removing the leaves. By the time you can see a colony, it's already propagating spores and spreading. It latches on, it grows for 3-5 days, then it starts producing spores. You can't reliably see the initial infection with the naked eye.
Good news -- if this is indoors it'l 99.99% self-inflicted. Either you are getting condensation at a consistent point in your daily cycle, or you are needlessly foliar spraying the plant and consistently have water all over your leaves. Don't do that.
RH% can spike after lights out due to temperature drop. This is the most likely time it is happening and you won't notice without a probe to measure RH and you can check it without interrupting dark cycle -- a wireless one that connects to your phone is very useful.
I speak from experience. I tried all that stupid shit up at the top and none of it works. Just makes it worse. I was trying to grow too large of a canopy relative to me dehumidifier's ability to keep the humidity in check. I didn't fix the problem until i cut my canopy size down. this allowed my dehum to keep up and also reduced my 'daytime' temps so the drop after lights off was less severe.
Check a dewpoint table. if you are 30-32C during the day and 55-60% RH or even high if you shoot for a more proper VPD, you'll hit the dewpoint above 21-22C or thereabouts.. above 70F, which is easy to hit after lights out. Now i'm at 27-28C during the day and my canopy is half the size, so there is significantly less transpiration occuring (plants release moisture), too. All of a sudden my consistent WPM issue that would occur around 4-5weeks into flower stopped.
I was so pissy at that time i nearly quite growing. I was fastidious about cleaning during this time, but at the end i was so pissed i didn't bother leading into the grow wiht half the canopy etc... even without cleaning i had no problem. Since then i've obviously wiped my tent down. I haven't had a wpm problem in 1.5 years. Indoors it's almost completely self-inflicted. Find a reason why and look inward, not outward.