Some brown is normal. Does the bottom have holes for good drainage? Loosen those ties on the stakes. Tight ties are for shipping. The tree will not sway and get strong.

Maybe its not clear from the photos, but the plants are planted in the ground.

With respect to the browning, this seems beyond what would be normal browning on a few leaves. as you can see in the photo, nearly all the leaves of the plant turn brown/dry on the edges and then wilt/fall off soon after the leaves emerge.

When the leaves die from the tips like that, the cause is lack of water. If it's old growth, it could have been a one-time stress that just left its scar. If new growth is lso browning, you have an ongoing problem.

Before you think more water is the answer, you need to keep in mind that that lack of water (to the plant) could be caused by root damage. Avocados are especially susceptible to root rot if the soil is watered too regularly.

I'm also just north of LA. I find that a 20 minute soak once a week - maybe twice when the temperatures get toward the upper 90s - is all the water my avocados need. The soil dries out between waterings. The root rot fungus dies back, but the avos can take it. If you have been watering daily, let the soil dry out a bit.

What kind of soil do you have, and how is the drainage? In my hard clay soil, I started growing avocados by digging my holes 4 ft diameter and 3 ft deep, and mixing the clay 50-50 with organic matter. Wire gopher baskets too, just like yours. Even those measures were not enough. The clay just became a 4' diameter pot that retained the water and drowned my trees. I needed to dig drainage ditches from my holes in the downhill direction, and backfill the ditches with 50-50 OM too.