purple stems in flowering - overfert??

First of all, I have other plants in the environment that arent purpling, so im pretty sure its not the temps.
Is purpling an intial symptom of overfertilizing? I know that burnt tips are but Ive read around a bit on this subject and the general consensus is cold temps/genetics

Jack herer from Tacoma dispensary btw, ffof with a tiny bit of dolomite.. using tiger/big bloom adjusted to 6.5 to 7ph
good lookin out

Genetics or maybe that plant did get cold some plants can take the cold better than others.