That is the way with trees. They look fine for 20 years running and
then suddenly they start to keel over. If it looks stressed you should
react. And it is a one ton tree, so it will want tons of organic
matter.

For the time being I've been taking leaves and such and piling them in the
area directly around the trunk. Before winter hits, I'll be doing a lot of
work re-landscaping the yard including mulching the whole front yard over.
We're also planning on catching rainwater from the downspouts and funnelling
them out to the yard over time.

James