Bleaching on the top colas is a common sight in sativa grows under strong LEDs, because the plant keeps pushing toward the fixture long after the grower stopped raising it. White, terpene free tips are the giveaway, and by then the damage is done. I follow the hanging height table on https://hazesativaseeds.com for the last four weeks, which recommends more distance than the LED manufacturers suggest for these strains. A dimmer on the driver is worth more than an extra 30 centimetres of tent height.