Do you clarify regularly to get rid of buildup? Buildup might be causing dullness.
Also rinsing your hair with freezing water after conditioning and detangling will seal the hair cuticle, preventing frizz and encouraging shiny locks!
One trick I have found is adding in oil in the morning and as a refresher will add great shine. hope that works for you too.
Try using an oil, like Jojoba, along with your styling products