Yea that is pretty red. However, its my experience that red or purplish stems aren't always indicative of Mg deficiencies. I have vegged and flowered many strains that show this pheno. Flowers always turned out very nice and robust. This isn't a guarantee that it isn't a Mg in your case, just sayn my runs have always been great even with red or purple stems. But like SM said try a foliar app and wait a few hours if it clears up then it was a Mg thing. Use foliar as you will get a quicker response.
FWIW
I had procured some DJ short blueberry beans several years back from harborside Oakland, I popped 1 and lost the pack, but that one was fem and the branches were solid purple start to fin, calmg or not. Was wonderful structure and flavor
its either a kush lineage strain you got their, or its an mg deficiency. If its a problem with mg, you can easily fix that using epsom salt. Great solution if you're on a budget...