I have been following the posts you make on your orchard. It sounds like it’s a tough area to grow apples. Perhaps try some of the old apples of the South or look at modern apples that resist Summer rots and put them in a test plot?
I also find diagnosing Summer rots to be challenging. Last year I had 50% of my Enterprise apples had some kind of Summer rot. I thought it might be bitter rot but the fruits never developed the characteristic v-shaped lesions. Instead it was mainly a surface problem with most spots less than a 1/16 inch deep with a few a 1/8 of inch deep. I hope this year it will not appear or at least that I can identify it.
Here is the post with good and bad apples.