I’ve had this cactus plant for almost 8 years and it just recently started developing these black (mold-looking) spots. They are in an almost straight line going up the plant. Maybe 6 or 7 spots. I have had him in the same pot for over 5 years and it doesn’t have drainage.. which I’m aware is probably not the smartest with a cactus, but since he had always been growing and having no issues whatsoever, I didn’t see as too much of a problem. Am I going to lose this plant? Do I just need to replant him in a draining planter? THANKS!