Need some advice on RH problems!!

So my grow room is 5ftx3ftx7ft tall.

Sealed room with a passive 6in intake with a 6in booster fan.

6in inline fan for exhaust. one 16in oscilating fan.

the 16in fan i have running 24/7. i have the booster fan and exhaust fan hooked up to a theromast, to maintain my temps.

The problem im having is my inline fans dont run at all during the dark period and im getting a steady RH of 75% when the lights are off.

My temps seem to be prefect at all times and the RH is perfect when the lights are on.

Just trying to figure out a way to run my fans so i lower the the rh during the dark period should i have my booster fan on the intake run 24hrs, it will lower the rh but afraid it will lower my temps to low, my intake air is from the outside and has been cooler weather.

so im in a little pickle i have been just manually turning on the exhaust fans 3 times during the dark period to lower rh.

if this doesnt make sense pls ask questions need to figure this out!!

well i just let everything how it was but put the 6in booster fan on a timer, to push fresh air in so it lowers my humidity.

I have it set to run non-stop during light hours, and during the dark period it runs for 30mins than off for 1 hour.

I think that will solve it i just dont want the mold!!!