Problems with large, 30 year old japanese Acer.

Hello,

My mother has a beautiful Acer tree in the garden, for years we have just left her alone and had no problem, last year we removed a sucker and early spring we removed what had grown back of said sucker. We are now having a problem with the Acer and no idea what to do, my mother is quite worried that it is going to die off on her, this tree is a 1 in a million.

One side of the tree just seems to be dying off, leaves curling dead wood etc the tree itself has also grown an awful lot less this year she is usually a lot more bushy, fans out and drapes onto the patio, this year we have never seen anything like this.

I have attached pictures of what remains of the removed sucker, the damage and the rest of the tree

Damage:


Sucker:


"healthy" side:


hopefully someone here knows what is up, any advice is really appreciated thank you so much.