First Grow In My Brand New Room. LSD and Cookies Kush

Well I'm extremely excited to finally have this room up and running. It has come a long way from the space that it started as. Here are the specs:

10 x Barney's LSD
7 x Barney's Cookies Kush
3 x Sun System LEC 630 240v
Hydro Crunch Light Controller/Timer
Can Filters Can66
Max Fan 6"
Oxygen Pot Systems Ebb and Flow Using Hydroton
Remo Nutrients
18000 BTU Senville Mini Split
Sentinel GPS CHHC-4i
Active Aqua 1/4 Chiller
70 pint Dehumidifier
Hydofarm Air Pump with 8 1.6" air stones

Seedlings are 15 days old, I am only running 315 watts in each light at the moment. PH 5.8, PPM 820.

Temp sitting at 80, humidity only 39. Should I get a humidifier? Also this is my first hydro grow. How often is everyone flooding in hydroton. Right now I have it flooding every 4 hours.