VPD target zone not attainable during "lights out"

For the most part I am able to sustain recommended VPD target zone for the girls when light is on. However, lately during the lights out period as temps drop a bit, the humidity isn’t falling much and therefor the girls are out of the appropriate zone for several hrs. For example, humidity today in my basement (and outside) was 75% all day.
It isn’t occurring every day, but I want to be on top of this as much as possible. And though I have to admit I don’t completely grock the science of VPD, I was provided a chart last grow to try to follow and adhere to. So my question stems around the issues that could arise if this continues.
For the record, when lights are out I have 2 fans inside the tent circulating air and 1 outside the tent door (which is always open) pushing air in the room (10x12). I also have intake & exhaust operating and about 75%. I have a small (grain of sand at the beach) dehumidifier in the tent that is definitely pulling moisture out of the air, but to no avail. I am not able to procure any more equip at this time, so I’m dealing with what I have.
I did try closing up the tent for lights out, but my intake is just pulling from another (larger) room in the basement. Exhaust filters into yet another room. So the humidity is pretty consistent throughout.
So, I guess I am curious about the detrimental effects of this situation. The girls look happy to me so I haven’t stayed up at night, but…
Any info, suggestions or light on a blind spot I might have will be greatly appreciated.

Pic is to illustrate set up. Screening covers door of tent.
Thanks in advance!