Q.Calla Lilly
Some of the leaves are turning brown and the plant is starting to droop even with watering

Browning flowers may be that they are at the end of their life cycle and can be removed from the plant.
Drooping plants can be due to watering issues, too much or too little.
Make sure the soil is well draining.
These links will help you.
https://www.gardeningknowhow.com/ornamental/bulbs/calla-lily/deadheading-calla-lily-plants.htm
https://www.gardeningknowhow.com/ornamental/bulbs/calla-lily/drooping-calla-lilies.htm