Sorry missed this question. Actually what you're seeing there is reflection from a blurple LED behind me - lol. Although the pheno bottom-middle comes, actually all my Blue Ripper phenos have purple stems and stalks, stalks are typically striped with purple lines. My take it's mainly genetics, I recently downloaded and read a bunch of articles pertaining to purple petioles and their causes and nothing came up with concrete reasons for them. I don't worry about it as many strains show that trait and if they're perfectly healthy otherwise I just attribute it to genetics. Most of my best phenos across different strains have them and I've noticed them on pretty well any strain with blueberry in the lineage.