These large fruit are increasingly at risk for Bitter pit.
Bitter pit is a physiological disorder of apple fruit.
I am sure that all apple growers have seen the dark sunken pits and brown corky tissue that are the symptoms of the disorder. It is generally believed that Bitter pit is a result of a calcium deficiency in the fruit. This is not always true since the tissue affected by Bitter Pit is often higher in calcium than the surrounding tissues. Unfortunately there is no quick fix for the problem. Calcium sprays are helpful in reducing the amount of Bitter pit, but other cultural practices have proved more effective in controlling the disorder.