Thanks for teaching me about the dangers of RH swings, I didn't know that was a root cause. I've never had mold issues before.
Yeah, simply put - fungi are opportunists. If your temperature and humidity swing around, they'll find the right conditions to germinate and reproduce. And they don't need much time to do so.
Outdoors, for instance, you'll notice mildews proliferate when the autumn climate starts peppering into the late summer climate.
I never had issues with fungi until my current situation. I knew the basement was pretty heavily populated with them, but it wasn't until growing that I saw just how easily they take hold.
It's almost impossible to avoid some fluctuation from lights on to lights off, so making sure you don't have stale areas (places where your circulation is ineffective) then takes precedent.
Concerning the device light issue - I have to doubt the amount of light emitted from most devices is enough to throw off your plants circadian rhythms.
But yeah, I would do what you can to have environmental controls outside the tent. And, as suggested, have an Inkbird or similar device to regulate those controls.