Plum Tree Problems

Help. I have had this plum tree for 5 years now. We had some issues over the last two years with black knot disease, but pruning resolved that and there has been no issues with that since and this year we FINALLY had 4 plums! Unfortunately, we have a new issue. Almost over night our tree went from healthy to dead. It is looks like early fall and the leaves are brown, curled and falling off. I cant see any cankers or obvious issues other than this weird pink/purple thing that when poked seems to crumble white spores? Any advice or if someone can point me in the right direction that would be awesome. I live in Mass and it has been and very wet summer.

Looks like it may be a slime mold and if so, likely not why your tree is having problems.

Apparently something has invaded the vascular system at the roots or trunk.  It may be the the growth at the trunk or the growth may just be taking advantage of the dead roots.  I often have death of Italian prune plums but it happens in the trunk so outlying roots come up as replacements. If this was a grafted plum then it could be that the roots were susceptible and it starved the grafted tree.
If you have seeds from the fruit you can try planting them or or select seeds from trees that thrive in your area.

Plum tree problems are numerous and varied, stemming from wind-borne virus, bacterial, and fungal spores that are also transferred by splashing water. Plum tree diseases can cause the fruit yield to be slowed or stopped entirely. As a result, manage plum disease as soon as possible after it is discovered to ensure the health of your fruit-producing plum trees. Often, plums die unexpectedly and for no obvious cause. I believe that is due to our hard clay, which does not drain effectively. It's most noticeable during wet seasons. When the tree's leaves begin to fall off, you can simply grip the trunk and pull it out of the ground with little effort. The roots have withered away.