I need help diagnosing a problem with my young pistache tree. It was planted last fall and has done well until the last few weeks. Some of the leaves turned very bright yellow. They did not turn brown at all. I had been watering it 2x a week with a hose for between 30 minutes and an hour. I think it got too much water. I slacked off the watering and started adding Superthrive. It seems better, but I'm not sure. Suggestions?