Q.Calla Lilys Care
why are the leaves turning brown on the edges

Certified GKH Gardening Expert
Unfortunately, there are many things that can cause this. I would start by testing your soil parameters.
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-moisture-in-plants.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/soil-ph-plants.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/test-soil-for-pests-and-diseases.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/making-sure-soil-drains-well.htm
This collection of articles will help you to care for Calla lilies:
https://www.gardeningknowhow.com/ornamental/bulbs/calla-lily