I left the country for two and a half months and left my cactus in the care of a friend. When I came back, apparently he had been leaving it under a desk lamp and not by the window to get enough sunlight (his room is very dark). He watered it with a splash of water and cactus food once a week, so that’s fine.
Now my cactus I’ve raised for three years went from having a healthy thick green stem to yellowing almost entirely. It feels thin and weak, and the top bends when I press it. Only two green arms are left on the sides. Is my cactus redeemable if I put it back under my pink lights at home, or should I cut and replant the remaining green arms before they rot too?