Apple trees

We have 3 eating apple trees; Katy, James Grieve and Jonagold. All 3 trees are looking really healthy and, between them, we have eating apples from mid August till Christmas with plenty to give away. The Jonagold is the late apple of the 3 and I just picked the remaining apples before the blackbirds, fieldfares etc. finish them off. All three have had superb flavour this year, don't know if it was the heat and sunshine. The Jonagold are almost like eating sugar lumps and are decidedly morish but most have to be peeled because the skin looks so ropey.
Would anyone know if this is just the variety, or because it is quite a late variety or any other reason and if there is a way to preveint the blemishes.
There have been a lack of grubs in them this year also.

Pictured is some of the Jonagold.