Dying Crassula mesembryanthoides?

last month

I bought this crassula a few weeks ago and think it is infected with root rot- it seems to have been grown in one of those sod things that holds too much water. I have reported by surrounding the right root ball with 1:1 sand/cactus soil mix. I recently plucked several black leaves off of it, and see some continuing to yellow. Some stems seem unnaturally brown- and there is a fuzz (fungus) where I recently pinched it back. It seems to have stopped growing. Is it a goner? :(