Wondering if anyone can maybe help figure out my issues. I suddenly had very large elm tree that filled out perfectly in the spring have all it's leaves brown and drop. Also appears that the bark is now falling off

As well in the front I have a Japanese maple which also bloomed perfect I. The spring but is slowly haveing it's leaves die off. The maple has been there almost 6 years now with no issues. I had a cut leave Japanese near by die off a few years before I planted this one. I have a large walnut tree that I think may be the issue ??? If there something I can look for to try to save the maple ? Pretty sure I'm out of luck on the elm.
I'm located in southern Ontario.
Thanks in advance