Both.
Kim Beauty I cut back every fall to refresh it but that root system is mature. The new leaves are more colorful. It doesn't work as well for other types but I find as long as the roots have corms developed, I don't lose the roots, and the plant puts up new leaves. It may take some time.
Some leaves just age and yellow. Sometimes leaves are dying back and coming up at the same time.
If you go past a certain point in letting them dry out before watering, they will get crispy but can come back from that. Same with cold temperatures. But sometimes they just die back and I'm not really sure what that final step is for perfection.
