Purple where light hits only

Just checked, I lied, a higher fan leaf is stiffer with purple on top side only... genetics? Let me know if someone knows!

...Actually, since adding the Epsom salt, my newer growth doesn’t seem to have this issue anymore, it’s all on the lower growth from before stretch. Might be too early to tell though once the age a bit more...

I have the same thing happening with Barneys Farm Glookies. Since it’s only on the top of stem, I’m inclined to think it’s genetic but I added a little Epsom salts for the magnesium anyway. My phosphorus level is good. RDWC grow with RO water.

It's such a grey area.. but I will try to explain the best I can.. Sometimes it's normal sometimes it's not. "Other signs of phosphorus deficiency include delayed maturity and reduced growth. Deficient plants may show purple coloring in the older leaves."... I have seen it and cleared it up by adding a bit of P.. The stocks that get the most light are the fastest growing biggest leaves.. They take in a lot to continue to grow. Plants Use P to support the transfer of energy not just to made flowers. Adding a light amount of extra P would be a a great idea. The extra P can't hurt... I hope this helps clear this up for you...

I would not worry about it, the strain could have purple in it late after flowering awhile or it is the way the light hits and reflects they look fine

Una leggera carenza di cal_mag

I am currently growing an AK48 autoflower that had me wondering the same thing. I noticed that upping the ppms would cease my stems from turning red. The part of the stem that turns red remains red indefinitely. There is no reversal. Some stems display both colors. Why does the plant show deficiencies starting from the top in this case? Not sure, yet. I have documented this and taken pictures. I run a hydroponic DWC system. Cheers.