Here is an example of what Gall Wasps do though the ones on my tree's leaves don't get anywhere near as big.
Edit: Having looked at something called Peach Leaf Curl, a fungal disease, I think that's more likely what is afflicting my Nectarine tree. Seems I can't do much about it until the fall or spring though.
The other issue my Nectarine tree has is the fruit eventually starts to develop clear crystallized sap. I have no idea what that is, it's probably a disease of some sort, but we'll see how it does this year.
Of two apple trees, I might actually get an apple off the thing this year. They're both fairly young tree. One is a Snowdrift Crabapple tree that has biannual blooming unfortunately. This is bad because apple have to be pollinated by other apples that are not their closest relatives. So my Gala Apple can't be pollinated by another Gala Apple. That's why we bought the crabapple which looks beautiful in the winter time with all it's red berry-like crabapples on it. The other issue is the biannual blooming. When apples produce flowers they produce a chemical that says don't flower. So having to many flowers one year results in no flowers the next year. This is solved by removing half the flowers... something I'll have to do in two years.
The Gala Apple tree has fruit on it this year thanks to the other tree flowering. But apples are among the hardest things to grow. Touring any super market in the US would leave you to believe otherwise though. All thanks to farmers spraying their trees every 2 weeks with chemicals. I don't intend to do that but we'll see what happens.
Something I might get fruit off of is the Fruit Cocktail Tree. Yet another crazy investment on my part. What I love about this gimmicky tree is there are absolutely no pictures on the internet of one. I'm starting to see why. Though my tree is loaded with fruit (a bit small for what they should be) I notice all of them have hair. Supposedly the tree has on it Nectarines, Peaches, Plums, and Apricots. Well Nectarines don't have hair on them so they're not growing. Plums usually don't have hair on them either as far as I know. So that leaves Peaches and Apricots. Assuming their picture represents the fruit varieties I'd say I'm getting 3 types of fruit at most.
I have a pear tree but it's afflicted with blight and had to cut off lots of the branches. Pears are developing on it but not many.
The native fruit trees aren't at a flowering age yet. They include 2 Paw Paw trees, Persimmon, and 4 Native Plums. The Paw Paws might flower at a young age and hopefully will do so next year, and the Native Plums might be flowering by next year. I hope to taste something at some point that tastes reasonably good.