after 2 years i can say they racing stripes i dont worry about,and that will go away in veg with a little extra P and K because for me the stems always turn green again when i put them in flower,i keep meaning to try the GO squid emulsion since i think thats a 2-3-1 and im betting that would go a long way towards minimizing the racing stripe....in 2 years of growing gg im not sure i ever had a single plant not racing stripe on me...The glue hates rootbound, and the more red the stems, the less happy she is. It is common. Stripes might go away, but if a section of the stem turns red, it'll not go back. I've tried different stress on a few... she shows her stress in red.
thats a classic pic of a rootbound gg4,what looks like a Mg deficiency is being caused my the rootbound condition,gg4 loves her leg room,up-pot that and it will go away quickly,no need to up your Mg levels,just transplant.