Not saying it isn't strain related, but in general and if you use Roots2Shoots or Liquid Organic Matter you will get reddish stems more predominate than normal. Even many plants in soil or using humics show the reddish pigment, which is an anthocyanin flavonoid that is a plant response to UV damage of heat intensity in direct sunlight. It is a stress related response but not all plants show it to the same extent. My nutrients will bring it out more than normal usually.
It is actually a good thing. Some plants do not have the proper micronutrients to create enough anthocyanin so it doesn't show in UV damage and light stress but if the plant does have it is light a protectant. I would rather have it than not have it as all indoor plants get UV damage but not all can respond to it.
NOTE
Anthocyanin replaces chlorophyll in the chloroplast, but only on branches, stems and even veins of leaves that are directly in the light. If a leaf is covering a stem and you lift it, the stem would still be green. That is when you know for sure it is the flavonoid. Chlorophyll absorbs blue and red spectrums and reflects green, that is why we see plants as green. Anthocyanin absorbs Green and Blue, and reflects red so you see red. I would always rather have my plants show the reddish pigment for two reasons. One, I know my plant has the proper nutrients to make enough of the flavonoid ( and flavonoids play a bigger part than growers know), and your plant now can absorb green another spectrum of light that is between blue and red.
Also will only be on top of branches and stems, not the bottoms again only direct light, so everything leaning is reddish and the ones straight up on have a little pigment.