Japanese Snowbell try suddenly dying

Hi, we planted a beautiful Japanese Snowbell tree in our front yard in North Vancouver 16 years ago. It was doing beautifully until just recently. I noticed in June that only a few branches had the lovely white blossoms. Now half of the branches have brown dead leafs and the other half have green leafs that are starting to curl. I am mystified and very sad this is happening. Does anyone have any ideas as to what has gone wrong and is it beyond hope and should I have it removed?

 

Any changes to soil compaction in the front yard?

 

The person who mows out lawn said they put done some fertilizer on the lawn that surrounds the tree. I also planted some marigolds around it. It's a fairly large 16 year old tree. Amazing how quickly it is dying.