Eucalyptus

[PurpleParis]

We have a double stemmed eucalyptus planted in our garden, we have had it for approx one year, it has grown quite well but in the last couple of weeks one of the branches seems to have developed a severe problem.
In the middle part of this branch the leaves turned a beautiful pinkish reddish colour but not have gone so brittle that they are falling off to the touch or the wind. The bottom is still growing and is green and the top is still green and healthy, the middle is now alost bare.
Could anyone please advise as to what the problem could be and if there is anything I can do to remedy it....thanks in advance.