humidity!?

I have a grow setup whic i am really happy with except i'm having problems with my humidity levels at night. i have 2 grow rooms(tents) both in flowering running 12/12 at opisite times, so when the light is on in 1 it is off in the other. the tents are in rooms right next to each other, when the light is on the humidity in each tent ranges from 40-50 but at night it ranges from 60-70 which is way too hight and i have just started to get some pm(mold). I can take care of the mold i just want to get the humidity in proper range. if i get the air from the tents outside would it be enough to have a d-huum running outside the tents, or do i need 1 inside each tent?