Leaf wilt can be caused by different factors. As a Haworthia grows, its leaves move slowly to the outside and will eventually wither. However in many cases, leaf wilt indicates problems and attention needs to be paid.
As a result of dormancy or self-protection, Haworthias allow outer leaves to wither to protect growth centers. Root rot, high temperature, short of water, and too intensive light are common causes and should be dealt with accordingly.
When Haworthias are less actively growing under low temperatures, overwatering can cause root rot which further leads to wilted leaf tips or edges for some Haworthia species.
Besides, Mealybugs bite leaves and can cause leaf wilt too.