Apple trees do tend to drop some of their young fruit at this time of year. It's called the 'June Drop' (even tho' its July now). I don't think it should have dropped them all tho'. It has been a very dry spring and early summer so it could be due to that unless you have been watering it. Shouldn't need feeding if you planted it with plenty of soil improvers. I would leave it to establish itself for 2 or 3 years then hopefully it should start fruiting okay.