for flushing you need to run i'd say at least 3x the volume of the pot (15g water in a 5g pot) thru at least 3 times to "flush" the nutrients out of the medium so it cannablizes stored nutrients in the leaves. it sounds like your medium still had too much fertilizer so the plants didn't need to eat itself. maybe start with 2 weeks next time and for the first 3 waterings flush it hard and let it dry out again. also strains can fade differently than others. some turn lighter some turn darker. it also depends what types of fertilizer you were using to begin with (synthetic salts, organic, supersoil etc)
you could take it longer if you think it might fade or just harvest whenever the trichomes are the maturity you want and know for next time. sup to you.