Too much sun! I keep my Haworthia away from direct sunlight, currently it's on a bookshelf 6 feet from a window and I've also previously had it tucked into a corner of a North-facing windowsill for a couple years and both of these locations have been perfectly fine. It could also be underwatering but I'd start with moving it to a shadier place.

Not sure if I can write this or not but, download the " Picture This " app. It will diagnose your plant.

Looks okay to me. Mine turn dark all over at times and they are doing well. Some are almost black.

They are under bright LED's. They never turned so dark when outside in the sun.

Yes, bit colored from light. Haws do not need strong light. And as Stush said, they will get really dark if too strong. Some haws have sort-of curling leaves; look at photos Stush posted.

Just make sure you don't overwater. It could look similar if rotting - BUT the leaves will be more yellow & will get more soft. They would eventually start falling off or can be pulled away easily. Looking at the photos, I don't think that is happening.