Macademia Drop

John Corney starts with ...
Hi, I have had a problem with my macadamia nuts dropping off when they get to half-size. I get a very good fruit set with hundreds of nuts and about this time of year (October) Most of them drop off. I have had a problem with anthracnose in the past but I have got on top of that as my mango crop is large. They get watered about every two weeks with a wobble sprinkler for 3 to 4 hours. This has been going on for years an I don't know what I am doing wrong . They get ck88 fertilizer four times a year. Am I using the wrong fertilizer? Is my watering program wrong or must I spray them with something? I live in Proserpine Central Qld. Thank You in advance. John