wouldn’t worry your self if it’s just the petiols (thats the stem that attaches leaf to branch, think I’ve spelt that right) chances are it’s just Gentics. If you find your stems/branches developing purple stripes try raising your light or dimming before you over fert with cal mag. Other tip for mag diff and to stay on top of it, mix up some Epsom salts (1 tbl per ltr) and foila spray weekly until 2nd to 3rd of flower.
