My sand cherry tree was growing perfectly fine until yesterday. All the branches drop down in one day. I have no idea what happened. I was thinking could it because of the rain from yesterday? Our neighbors’ gardener also came yesterday for their garden which is right next to us. Was also thinking could it be possible for them to accidentally put weed killer or something that would cause this?

Attached two photos for comparison. Left is picture when it was healthy, right is picture from today =(

Please help to save this plant.