I noticed a bit of yellowing earlier this year around the base, and figured I'd keep an eye on it. Checking on it today, it seems worthwhile checking if anyone here has any advice. The camera really amplifies the difference here, I had barely noticed it just by looking.
thanks for the input! I think a repot + fertilizing will help here tremendously. first searches for cactus yellowing only yielded results about rot which had me very concerned. this looks like it might just be nutrient deficiency though so I'll try solving that first.