Is there grass growing underneath the trees?

How much watering are they getting? What is the soil like? Can you post photos?

Your post asks a lot of questions like how were they planted? and why in the heat of the summer?

You do give your trees water in the Summer every year, right?

I think your down by San Diego where they have cool summers. We plant citrus all year long, but they require lots of consistent water to establish themselves in a new space.

Also it sounds like the trees went into shock when planting out. It helps to research before planting. New trees benefit from rich loose soil three times their pot size. Dig a tunnel around the planting and fill with water. Fresh compost every month. Keep trees watered for a year.

i use to mulch my orange tree twice a month with grass clipping. Since it was established that meant putting the clippings in a wide circle only at the outside of the plant. People on the East coast can't mulch with grass cause they have too mulch rain. But the brutal southern California sun turns them to dirt in two days.

My mother burnt the grass several times trying to use ammonium sulfate, i didn't use that.

We don't know if yours are dead, but it does sound like they are close. The rain we have had recently should have caused the trees to grow new leaves.