I can't change my environment. My demudifier runs 24/7 and the humidity is always around 50%.
You absolutely can change your environment, you may just need a stronger dehumidifier...
I'm gonna recommend checking the humidity in your tents, esp in the lower areas where you see it starting.
There's basically two factors that lead to mold and mildew in a grow: 1. Spores, and 2. The right environmental conditions for them to germinate. Since you already have PM, you're already not in a good place for number 1. There are way way more spores just floating around than there would be in a grow with no PM. Do whatever you need to to eliminate any existing PM, I'm not an expert on that. But keep in mind, the spores are literally everywhere even if there's no visible or actively-growing PM on any of your plants, even if you've never had PM before, there are going to be a few floating around here and there. You're never going to completely eliminate them, you just want to minimize their numbers by removing the primary sources.
Then you need to tackle number 2, which if you aren't measuring the humidity and temps in the areas where the PM is starting, you really don't know where you stand on that front. PM needs high humidity to germinate. That can happen in pockets near the bottom of the plants where there's not much air movement. It can also happen when there's not enough air being exhausted from the tent - plants put water into the air when they transpire, and you want to move that humid air out of the tent and replace it with drier air from the room. It can also happen when the lights turn off and the air in the tent cools - this is why outdoor humidity is so much higher at night, and why PM is much more common outside. Indoors you can reduce those humidity swings by cycling air into and out of the tent more quickly - the faster you exhaust, the closer the temps and humidity inside the tent will be to the temps and humidity in the room.
The closer you get to addressing those two factors, the less chances you will have of getting PM.
Personally, and for full disclosure, I haven't had to deal with PM on any of my grows, but I have gotten bud rot on multiple indoor grows, and the same method applies - eliminate sources of spores as much as possible, and get the environment in check to prevent whatever spores are left from being able to germinate.
Sorry for the novel, I wish you the best of luck in your grow!
