Fruit trees

All three can need pollinators, Pdh, another tree of a compatible variety to pollinate the blossom. What varieties do you have?

Yes, they're self-pollinating varieties, though even self-pollinators will benefit from a compatible friend nearby. Regardless, some apples can take four or five years to produce fruit. Our pear - not a Conference, a Coscia - took five years. It could be a case of immaturity. What have you fed them with?

Pollination has been poor this year because of the weather - too cold and wet for the bees. I had a similar problem on well established trees, lots of blossom and little fruit. Nothing you can do about it other than try to pollinate by hand next year but I would just let nature sort it out. It would definitely help your chances if there were suitable  trees for cross-pollination in your neighbours gardens though.

Bees do it better.  Self-fertile fruit trees will always do better with a compatible pollinator.  It might be better to concentrate on just one fruit rather than growing one of each.  Victoria is a plum everybody knows the name of but it is a challenging plum as it suffers from diseases. Conference is partially self-fertile.