oh cool, just read some info on VPD, never heard of it before. I do think I was facing a low VPD point before I added the intake fan. Now I am very confident about the air exchange in the tent, the growth rate increased exponentially when I added the fan. I bought a smaller sized intake fan vs the exhaust based on a forum. I then put it on a cycle timer, 5 on /20 off, so that the air is exchanged every so often.
Below is a picture of when the intake fan is on, swelled tent, and when it is off, awesome negative pressure.
RH levels vary from 50-65% during air flush.
I did just buy a moisture meter to help with the drying phase when that time comes, I thought that was going to be my rare tool lol.