mineral

Hi everyone. Sorry if there's a specific sub forum for this and I'm in the wrong place. Not the best pictures of the marks on the cactus because they weren't taken specifically for this topic. I'm a little concerned about the yellowish spots on the base of the cactus. I think there are a few new ones as well, but I'm not certain. They were there when I bought it, by the way. Any ideas?

Your writings are very helpful, Trout! Thank you.