Looks like stress, not potassium.If somebody could take a please look at my leaves. This is a sativa dominant 9 to 10 weeks flower I'm in week 5 to 6. If I had my own opinion it would be from too much potassium. I try my best to pH the water 5.8 to 6.5. not all of my plants are doing this.View attachment 4311879 View attachment 4311878