First Grow - Triple Automatic: Purple Haze, Apple Fritter, Purple CousKush

Week 2 and still alive, I'm kinda suprised. They also grow quite a bit the last few days, impressive (to me). I am currently trying to keep the right VPD for early veg. RH is around 75ish if the air vent is off, which is borderline in the VPD chart at 24-25°C. I want it slightly lower because I just learned about mildew and want to avoid it of course! Unfortunately it drops to 50% when I turn on the air vent. So I tried to play around a bit over night with turning the vent on every hour for 15mins (mechanical timer) or so, which led to a rollercoaster curve between 50 and 75%. Not sure but I think the plants don't really like that either. So I turned it off this morning and put an old passive dehumidifier which my wife had lying around for her car in the tent (this simple plastic containers with a bag of dry pellets inside). I will observe and see what it does. Last watering was 3 days ago with around 400ml each plant, substrate still seems moist an inch under the surface, I will wait a bit more. The leafs look a bit pale and the tips slightly yellowy and weak, could it be lightburn (currently 400ppfd) or windburn? I probably let the fan run too long/too strong for a while. I turned it off for now for the next hours.