We inherited old garden on south west slopes of NSW, Australia. Have now seen twelve months in the garden and the grapefruit tree, approx 20 years old with a very obvious graft has not produced yellow fruit. It has many small and large fruit at all stages of development but green in colour. Thick pith, rind soft to the touch. We fed 2 handfuls of sulphate of potash plus a few teaspoons of epsom salts in 10 L watering can around the drip line 7 days ago. Is it a wait and see situation or is it a dead duck?