Different spots on yellow part of Grafted Moon Cactus?

Question

I just recently got gifted a Grafted Moon Cactus (I’m pretty sure that’s what it is called but correct me if I’m wrong please.) with a yellow top and I’m new to caring for things like these so I’m not sure what to do.

First, there are a few little black spots on the yellow part of my cactus. In addition to this there are, on the bottom of the yellow top part that extends out, spots where you can see it fading? Decaying? It’s incredibly lighter than the rest of the yellow and looks dead or dry? It’s not much yet but I’m scared that whatever it is will spread throughout the rest of the yellow part.

What do any of these spots mean and what do I do to fix this? Is there maybe anything else I’m doing wrong by the look of my cactus too? Also keep in mind this is being taken care of indoors but if it needs to be brought outdoors for any specific reason, I can do that even if it isn’t preferred. I apologize for so many questions but I’m fairly young and so new to this and am hoping I can get the answers I need.

Answer 1

Most likely you have fungal issues. Spraying with a fungicide should help. Here is more information:
https://www.gardeningknowhow.com/ornamental/cacti-succulents/scgen/fungal-lesions-on-cactus.htm

Here are general care instructions for moon cacti.
https://www.gardeningknowhow.com/ornamental/cacti-succulents/moon-cactus/care-of-moon-cactus.htm