Modern high power LED fixtures can deliver more light than some strains can actually use. Sensitive genetics may show bleached, pale tops close to the lamp, while others handle intense light and turn it into denser buds. I checked light tolerance comments on a few pages at https://budweedseeds.com after upgrading my fixture and noticing bleaching on an older strain. Raising the light or dimming it usually fixes the issue, but matching strains to the setup helps from the start.