There has been a heat spike here in the last week, well over 100 and approaching 105. I had rigged up burlap shade cloth several weeks ago and fearing the sun would be too hot on the resin containers, I moved them behind my shed several days ago so the trees get sun during the morning only however I came out to this this afternoon. These leaves are from one 24 hour period and that's the worst I've seen.

Some back story. The leaves have been yellowing and dropping for months now. I have tried watering more, and less. The pots are never dry and the potting soil several inches down will be moist, not wet. I have fertilized with grow power flower and bloom, and also with water soluble miracle grow, the miracle grow in half strength form. This nectarine has been the healthiest tree till today.

I'm assuming the trees are goners at this point. With so few leaves remaining and those in poor shape, I may not have the knowledge to grow trees in containers. Future plans will be to keep them watered and shaded till winter, adding some miracle grow if I see any leaves starting to push. Is there any advice for this dejected beginner?