Are you running your in-line fan with a controller? if you are not running it with a controller like Nug said pick up an extra humidifier, then run in line on lowest setting. It’s about your only option if you absolutely have to run your in-line fan 24 seven even though you’re an early veg. I personally wouldn’t run my in-line fan constantly in veg just often enough to cycle with fresh air every so often. This allows me to maintain a somewhat steady CO2 range as well.