Looked great until about 3rd week. Did have a problem with FN and temperatures have dropped. Can someone provide some insight from pics possibly. Also any guesses on strain? Thanks.
How cold is it? Low temperatures will detrimentally affect the root system and the uptake of nutrients, particularly in the case of magnesium. What nutrients are you giving her? Is it just those leaves that are yellow? Can you take a pic of the entire plant? Might be a little easier to seen an overall picture
BUT truely purple stems are often caused by genetics. That doesn't mean anything is wrong with your plant.