I've been on holiday for 2 weeks, and today I put my cacti out into the sun for the first time in a 2 weeks. I noticed immediately that one section of one cactus had "deflated", or collapsed in on itself. You can see white spots on here.
As I carried another cactus it snapped. I was carrying it gently, not forcefully at all.
I inspected it and have seen some white spots on them, which I never noticed before, though admittedly never looked too closely. I have read that these may be insect infestations.
I attach some pictures for your thoughts, but my questions are really
1.) How do I treat? 2.) Can I recover the snapped section? If so how? 3.) Should I keep existing healthy Cacti away from these?