deficiencies

Why are my leaves turning yellow in my hydro stystem?? They are not drying out but they are turning yellow?:reading420magazine:

Here is my situation. Grow Medium: Hydroton System: Waterfarm Buckets Nutrients: Humboldt Natural Grow and Bloom Water: Tap (190 ppm) Lights: 1000 watt dual arc, 1000 watt daylight (Large A Wings with super spreaders) Temp/Humidity: 65/76, 20-35% Strains: 3 Affgoo and 3 Skunk #1 So...