Dead fruit trees

[raking]

I have two 3 year old apple trees that look to have died and one two year old plum tree looking the same. I have one mature apple tree that delivered 250 apples last year and has 5 this year. My neighbours cherry tree also looks dead.

All the leaves on the "dead" trees just turned brown and fell away and their is no sign of life on them at all now. Does anyone have an idea what could have happened? After lasts years smallish crop on the new trees I was expecting a bumper year. The blossom was prolific back before the frost in April, but should this frost have "killed" the trees.
Finally how do I determine whether they are dead or just very ill??

[raking]

[saddad]

Have they been waterogged at all?  :-\

[bridgehouse]

Don't know if this helps but my plum tree died last year, some years ago I had a pear tree die in the same spot. I think that had a white fungus in the ground around the pear tree. it was years ago, so I planted the plum in the same place thought it would be o/k, it was fine for two years then the same thing happened to it that is happening to your tree,
  June.