The leaves are curling in on themselves from the side of the leaves going inward. Also there will be a water droplet hanging from the end of some of the leaves at times after watering the plant.
My Calla Lily Indoor Plant Has Curling Leaves, Why
Certified GKH Gardening Expert
Curling leaves are an indicator that the plant is not getting enough water. While you may be watering regularly, the water may not be penetrating the rootball. You should try soaking the pot in water for 5-10 minutes to make sure that the rootball is hydrated and so it will properly take water in again.
Also check the plant for pests. They may be sucking water from the leaves, which would also cause the curling.