What you had was a mutant Gymnocalycium mihanovichii, cultivar 'Hibotan'. It has no green chlorophyll, so other pigments are visible, causing the red color. It has no way to feed itself, so it is grafted onto rooted stock, typically a Hylocereus. The 'ruby ball' cannot survive on its own. Since it has rotted, all you are left with is the relatively uninteresting root stock. Gymnocalycium mihanovichii cv. 'Hibotan'

You need to cut off all that rot ASAP, before it spreads. Cut up until you see completely green growth, no rot. You will have to let the cut dry for a week or so, before trying to root it. No water at all until you have roots. Christopher

Rachel, it's very hard for me to make an assessment when I am not physically there to examine your plant. I don't quite understand what you mean by soft but not overly. I see that your last picture you had lost a couple of stems, so perhaps if its really rot setting in the base, you need to catch where is the rot happening at. If it's right under all the stems towards the roots, you are better of cutting off as much rot/brown portion as possible until you see healthy green stems, and try to root the cutting as best as you can. At this point, you can try to snap 1 or 2 healthy cuttings at the tip end towards the base. Always let the cuttings dry up and callous before their to root them in new soil. And also make sure when you snap them apart, the stem must be close as to the root base as possible, if you can snap some roots with the stem even better.

Than thats normal..... A rotting cactus tissue breaks apart easily, and is either hollow or yellowish mush. You have a combination of corking( natural aging process with cacti), and shriveling(process when cactus is kept dry or cold, but not damaged). Though, just to be on the safe side, check the bright area between the wooden and green parts of the plant. If there is rot, its most likely there. If there is nothing out of place, re bury your plant in soil.