Hey @3rd_i just caught up on your thread. A couple things, if you don’t mind me throwing my 2 cents in the hat.
9 plants and a small humidifier is going to be REALLY tight in a 4x4. Just my opinion. I grow 6 in a 5x5. We all grow a little different. That’s the fun part!! Finding what style YOU like best.
I try to stay close on VPD. Some times I’m way off. But ideal VPD isn’t necessary to grow a nice plant. I know many growers that would never run their humidity as high as you need to for VPD. Still grow killer plants.
None of us are perfect and all have made a ton of mistakes. That’s how we learn!!