Underfeeding mg deficiency or just Genetics ?! PICS

I'm just transitioning from veg to flower and my plant has started to develop purple stems where the new growth is pics follow ....
Is this lack of npk mg def or just genetics some of the leaves appear to have slight pale green areas at the top not badly but it's noticeable. advice needed thanks

I'm growing some Bubba OG now that do the same thing... perfectly healthy.
I've had genetics do this in the past too. IMO, no big deal.
If you are having def, lockout or toxicity issues.. the leaves will tell you.
How do the leaves look?

That wat i was hoping, good apart from some of the top leaves looking slightly bleached almost a pattern but barely visible, The plants growing just fine, I'm hoping its just genetics in that case and the leaves slight bleaching from the light as the plants quite tall despite being super cropped, any other ideas ?
thanks

I've heard people call bleached tops iron def...