Haworthia koelmaniorum, I guess it is Haworthiopsis these days:
It actually looks I have a couple of older leaves that have a similar looking issue that some of Steve's plants have.... This is an old photo though, so I'd have to go look and see if it is still happening. No clue how that happened. Certainly not sun related as this has always lived under at least 50% shade cloth if not more shade.
This can go really dark, almost black in coloration.
I am really bad at keeping an eye on my Haworthias, not sure why... maybe because generally as long as I water them and do not give them too much sun, they tend to be OK, not great, I definitely have pots with significant die back, but OK in the sense that there are enough offsets to keep them going.
