Certified GKH Gardening Expert
Usually this is due to a watering or nutrient isuue, but since you've been giving it plenty of water, you can probably rule that out. You may want to have your soil tested to see if it's missing something and then add the nutrient it needs.
Additionally, if it has been getting a lot of sun or wind, it could be scorched, which will clear up on its own.
Finally, if the brown leaves are beginning as spots and spreading throughout the tree, it could be fig rust. This article will help with that: https://www.gardeningknowhow.com/edible/fruits/figs/figs-disease-rust.htm