Hannan, does this dsease infect only the surface or does it cause rot to the flesh? Has anyone told you that it looks like black sooty blotch, not black sooty mold? If you are still with us and reply, I’ll tell you more about this pretty common disease of apples.

to much iron in the ground

If it is sooty blotch - and that diagnosis seems quite likely - then it has nothing to do with iron!! The disease is caused by a couple of fungal organisms and appears more frequently in warmer climates and areas with high summer humidity.

There are a number of extension service fact sheets published on the topic and they are worth researching to determine the most effective treatment options for your area.