What is wrong with my flowering cherry tree?

Hello, fellow gardeners!
I have had a small flowering cherry tree in a pot for 3 years. Everything was fine with it until a week ago when suddenly it became miserable with brownish trees. It was neither too dry nor overwatered. I fertilised it but it didn't help. Have a look at the pictures please. You can see in the third picture how it looked like in blossom in spring.
Any recommendations will be appreciated.

 

As the leaves have not dropped, my thoughts are its leaf scorch.

Leaf scorch | The Morton Arboretum

 

As the leaves have not dropped I always assume the wood is dead, usually live wood drops dead leaves, apart from a few exceptions in autumn.

Personally I think it flowered then died.

If the leaves eventually fall off, it might come back, but will be a bit worse for wear I think.