Humidity during dark cycle

I have a roughly 4'x4' living soil bed in a garage tent. Once the lights turn off my humidity rises significantly due to my inline fan turning off because the tent doesn't need to be cooled from light heat anymore. My VPD goes from 1.3 during lights on down to .3-.5ish when lights are off. I know this will be an issue when i flip to flower so im questioning whether i should put a dehumidifier inside my tent or if i should keep the fan running overnight. The temperature in my garage where the tent is will keep the humidity in a good range but it will drop the temp in the tent almost 15 degrees. So:
1. Dehumidifier controller with an inkbird
2. Run inline fan overnight where I get a 15 degree temp drop but it helps keep the RH down?
Big swings in Temp/Humidity are one of the main reasons for getting Powdery Mildew
I agree with 100%. I tried everything to combat the PM with little success until I got my environment dialed in to be about 5 degrees difference from lights on to lights off and that solved the problem. Even running very low humidity didn’t fix it