Poplar tree

This is the poplar tree in the house paddock. Looking dry and the leaves have gone brown with just tinges of the butter yellow it should be. It is also looking as though bits are dying and there is a split in the middle instead of its normal pyrimid shape.
I have done a lot of deep cleaning, so to speak, not my whisk over the top and didnt get very far.
The plumber was out to fix a blocked drain, we hadnt worried too much about the washing water going into the garden with the drought but the loo was threatening to block too so the septic had to be looked at, all ok thank goodness and all fixed now.