Reason for edible chesnut sudden death?
 

hi,

bought two edible chesnuts from reputable nursery. Last year one developed yellowing leaves which then became brittle brown and within a week the tree died.
This year started well with the remaining one but all of a sudden this went the same way last week - see piccie.
topsoil is 6 inches loam, underneath is all sand. climate -20 winter + 30 summer - we sometimes have really horrible wind. i watered the same as the other fruit trees i had recently bought (they are fine).
gutted - i love chesnuts and was looking forward to a brother and sister developing a fruitful relationship, alas now not to be.

Any possible reasons for their demise?

thanks

karaman