Desert Raven: Problems

I have quite the collection of cacti. Some are experiencing problems. Whether its overwatering, frostbite, sunburn, possible root rot.
Some are cureable,
Some will have permanent scaring,
Some have to be replanted Right away.

The following pictures are of the cactaceae plants I have that seem to be experiencing some issues;

Below: Madagascar Palm: bloating, bulging aound trunk,
Diagnosis: Becoming too dormant to absorb water supply,
bulging due to overwatering,
Treatment: Stop watering! Continuing to water will cause root rot.

Below: Cardon (Right; Black spot, Left; Bloating)
Diagnosis: Stem Rot/Black root rot, Dormant Cactus not able to absorb water supply due to lack of light.
Treatment: Cut off discoloration/ yellowing of the root & stem put in dry soil/stop watering,
if it continues to rot, you can get an anti fungal powder to attempt to save the plant,
Best advice is to cut your losses and throw it away before the fungus spreads to your other plants.

Below: Pup from a Haworthia turning purple
Diagnosis: Usually cacti or succulents turning purple means either it needs a little water, over exposure to light, or damage to the root
Treatment: Spritz with water until soil is completely moist (but not so much the bottom is sitting in water, just enough to moisten the entire top part of the soil)
wait a week for improvement, if none, try repotting into a larger pot (roots maybe cramped) or the other two irreversable; root damage or sun damage (which is scarring).