Hello 👋
I'd say bring in some light feeding being 3 weeks in, sometimes high light levels can increase the need for cal/mag/potassium. And I'd bring in a light calmag supplement with your npk, the yellowing between the veins can be a good sign of needing magnesium.
Also you could lower the light hours down to 18...since they're already raised fairly high in distance.
Happy growing.