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.

looking into it, I think this is likely the problem. I got a way oversized pot initially and haven’t noticed how much it’s grown to fill it, and haven’t repotted it since inital potting so it’s definitely due for one. thanks :)