What is weird is that the tops of the leaves are yellowing as opposed to the bottom leaves usually seen in N deficiency. Are you sure its not something else like heat stress? Also, your PH seems too high, try 6.0-6.5 for soil.
Mr. Happy Reviewed by Mr. Happy on . Yellowing Fan Leaves Indoor Soil Medium: Farfards Professional Soil 70% soil, 30% perlite Water source: Tap Water Source water pH: Straight from the tap - 7.5 Age of plant: Week 4 of Flower Type of fertilizer: Technaflora Recipe for Success Rate of application: 1/2 strength every other feeding Lighting source and distance from plant: 306 actual watts CFL, < 3" Temps: 75-80 degrees, 60-65 degrees Rating: 5