My Dad's 28 years old Monkey Tree has suddenly started going brown over the last few weeks. We live in England. He has tried to cut off the lower branches to aid the higher branches. The trunk also appears to be turning a brownish colour. He has recently put some weed killer on the grass which I think could possibly be the cause, but he has been doing this for years with no adverse effects to the Monkey Tree. I was wondering anybody could identify if it is dying and what may be the cause?