Leaves turning purple — problem or genetics?

Looks like a classic case. Check your pH first — 90% of these issues trace back to pH being off. Even small deviations can lock out nutrients.

Had this exact issue last grow. What fixed it for me was flushing with pH'd water and letting the soil dry out before feeding again at half strength.

Environment is key here. What's your temp and humidity? Sometimes the symptom looks like a nutrient issue but it's actually environmental.

Same thing happened to me when I was overfeeding. Backed off the nutrients by 50% and new growth came in healthy within a week.