I ran a 1000w HPS eight inches from my canopy in a 4x4 tent for three weeks in flowering. Never saw plants yellow from the top down before. It was like reverse N deficiency. Haha.
It can cause bleaching and alter the terpenoid profile. To the extreme it takes the potency away. I just figured it out on my Chernobyls. Had a 1000w hps at 8 inches from canopy. Lol. Took it to 16 inches and it hasn't gotten worse.