No more fertilizer, way more water. I think the leaves are a bit sunburned, but that should pass. If it continues worsening, construct a canopy of shade cloth over it.
How much water? I can't tell you exactly, but a gallon every other day is definitely not enough in your climate. One rule of thumb is to water a newly-planted tree with 2 to 3 gallons of water per inch of its trunk diameter daily. But each tree's needs depend on climate and conditions so I'd consult a local grower or nursery. Keep it heavily watered for the first several weeks at least in intense summer heat, then keep it generously watered for the rest of the first year.