Faint Purplish Spots

So I run GH nutes.. very similar line up to you when I’m flowering. I have the flora trio, plus armor si, liquid kool bloom, and calmag. My numbers are similar to yours, for photoperiods - and I’m pushing 1000ppm when it’s all mixed up.. so I can’t imagine what you are running is only at 600. Point being, I think this is over feeding. Some autos are temper-mental with excess feeds. Like i said this is similar to what I run for photos, in coco, and I try to keep it around 800-900 max for my flowering feeds. Of course it depends on your water source, I use tap that’s around 100 PPM. I’m not sure of the exact cause of the symptom shown here but I’ve seen similar from over feeding. And that liquid kool bloom is especially potent. Hope this helps.

@OuterBanks hi mate looks likely it is lacking in potassium after the flush add more potassium to the nutrient mix