What's going on with my cactus?

[YerAWizard]

I'm fairly new to cacti growing and so I'm not really sure what is happening. I've had this cactus for a year and got it as a nice decoration, but I recently left it with a friend for a few months while I was away. When I came back, there were sort of brownish patches all over the cactus. I've researched corking, but it doesn't seem to fit the description. It kind of looks like it could be scratched off, but I haven't tried it. I'm not sure if this is fungi or something else. Anyone have any ideas/can help me?

[teo]

I would guess: Some kind of spider mite damage

[iann]

Could be a number of things, but mites would be my first guess too. The skin is scarred, don't try scraping it off. There are some signs of growing out, so the mites might be gone, but look as closely as you can and see if you see any. A magnifier or good macro photo would help spot them.

[YerAWizard]

Do spider mites only attack one kind of cactus? The cactus is actually in a pot with 2 other kinds (again, cactus newbie so not sure what kind), but the others seem fine.

[teo]

The other plants are not cacti, they are aloes. In my experience it's mostly cacti that are attacked (among the succulents).