The other possibility is that the tree is a different variety which is unadapted to your area. Again the best bet is to get a new tree. You probably want to move over a little bit when you plant the next tree. Also examine the root system for evidence of injury. The roots should be nice and white.
Harvest time varies with individual tastes and locality.
One may consider a fruit ripe while another individual believes it is immature. However, fruit picked too soon does not store well and does not develop full flavor. Also the background color changes from green to yellow. Generally speaking, as red apples reach picking maturity the green peel becomes slightly yellowish. Green or yellow varieties change from green to creamy white or yellowish as they reach maturity.