What is the reason for the poor extensibility of blueberry leaves?

Typical water shortage or high temperature, I don't know where you come from. If you do this all summer, I believe that some of your blueberry trees will die, and if it is serious, all of them will die. I have a preliminary look at your potted plants, and I have the following questions:

First, the soil where blueberries are planted. On the surface, the soil is definitely not good. No, it's all loess, and the organic matter content is too low. Blueberry is a kind of fruit tree and needs a lot of nutrition.

Second, you put it on the hanging balcony, and the roots of blueberries are only in the middle of the flowerpot you use. The soil you use has poor water retention. Make blueberries dry easily.

Third, the weather is hot now, so we must water it frequently and give it proper shade.

These are some common reasons why I found blueberries appear in the above picture after looking at the picture.