2 possibilities, either Black spot or Bitter pit. If the spots appear early on and the leaves have the same markings then the former. If the marks are only on the fruit and/or inside then the latter.
If the fruit is small then it sounds like the tree needs a good feed to begin with. Then you could try spraying with Copper sulphate according to the info on the packet.
If it is Bitter pit then it is the soil which needs treatment. This is caused by a lack of Calcium. If you can get it, sprinkle Calcium carbonate round the feeding roots of the tree, again as per the info on the packet.

Should add that Black Spot is also known as Scab.

Welcome to Goy, have you checked out the blogs as well as the questions, they're enjoyable to read

Apple Bitter Pit isn't usually an issue provided the tree has sufficient water supplies when its fruit is swelling. As your fruits have been small in the past, most likely insufficient water is the cause - drought like conditions means the tree cannot take up calcium from the soil, even if there's plenty in it.
If you have apples this year which are brown spotted, have a look at Apple Scab to see if the symptoms match - otherwise, cut one or two open to see if there's any entry tunnels or any larvae or insects inside them.

Many thanks