One of mine did that when it was underwatered. It closed in on itself. It opened up a little when I started watering better, but never really full recovered. You can still see the wrinkles from when it was dry and curled.

San, need consistant deeply watered all summer, like once a week, the roots are waiting for you to water them, and will dry up if water does not reach them in time. In Winter I suggest that you barly water them enough to keep alive, established plants can go six months with out water during the winter monehs, and yes they dry up and return to their beauty when you start to water again in the warm months. In the Spring take them out of their pot, toss out what is not good remove dead dried leaves, rhizomes, and start them over. Don't toss out plump healthy rhizomes. Toss out old mix it is useless. Start with fresh mix that drains well. No Peat Moss it will stay wet around the base of the leaves. Fertiize 2 weeks after it has been replanted. Start with damp soil. I use Osomocte you use anything what works for you. These are the easist plants in the world to grow, there should not be any diseases , Period. Norma