Grapefruit tree advice needed
 

My 20 year old HUGE grapefruit tree is producing
many bad looking fruit. The new young not ripe crop
looks OK.

Problems with some ripening fruit a
1. Some of the outer rind has dark brown spots
varying from size of a nickel to
as large on a fruit as 1/4 of the whole fruit.
The rind is very tough leather like where dark.

2. Some fruit has small soft mushy portions.
No sign of rotting inside.
Taste is sort of spoiled.

I do need help. This tree needs fixing and I value it very much.
Thank you, Dave