Hello Nick, happy to help.

This looks like pple scab, a common problem during cool wet springs like we've been having this year. It's rare for apple scab to do real harm to your tree. Practicing good hygiene is the best approach to keeping it under control this year and into the future. The best remedy is to clean up all the fallen leaves and fruit as quickly as you can while it's happening. And then clean all the leaves and fruit that fall from the tree in the fall. The spores on the tree's material left under it can splash back up and cause more fungal symptoms. Those spores also overwinter on the ground (if the leaves and fruit aren't cleaned up) and reinfect the tree during next spring's rain. Be sure to dispose of the debris by burning, burying, or hot composting. If you compost be sure your compost reaches temperatures that kill fungi and weed seeds. If not, sending your yard waste to a city processor is the better option.

Here is more information about apple scab.

Good-luck!