I have just recently noticed that my weeping camperdown elm has now turned black and the bark is falling off of it. I have noticed the branches are very brittle and break off easily. I have had this tree for seventeen years and during its previous years has been plagued with leaf miner. Has this tree finally died? I live in the Brantford area and our soil is quite sandy but have amended the soil when it was originally planted with triple mix.
Since you mentioned that your tree has had previous infestations and the darkening of the bark, I’m inclined to believe that your tree is suffering from Dutch Elm Disease. Here is a link that describes infestation and treatment.
https://tidcf.nrcan.gc.ca/en/diseases/factsheet/10
In order to know for sure, I would consult an arborist. It may be too late but at least they can tell you if your tree is dead or if there is a chance it could be saved.