In flower I like to run higher PH levels in hydro, soil, coco, with all nutrients. In my experience.I would agree with Gweedo, looks like nute burn and perhaps mild PH issue. I don’t think I would lower the PH though, flush with plain water, cut back on the nutrients. PH nutrients to 6.3 for a couple waters, see if she perks up. Just my two cents, not a pro, just an average guy.