I'm sorry it has been a busy weekend. Here are a couple photos. If you need more or a closeup, just let me know.
This is the best I could do
I tried to send 4 more images but I don't know if you got them all. Leaf 1 image is what appears to me to be normal. Leaf 2 shows a small twig with fruit that appears to be dwarfed and diseased. Leaf 3 shows a twig with brown rot ( this is not normal on all of the trees. and Leaf 4 show a small twig with stunted yellowish leaves. This is pretty baffling because these trees continue to bloom every year, but never look really healthy. The soil here is just standard Georgia clay but it is pretty rocky. I have read where these trees can only live some 20 or so years however I have seen them with a lot bigger trunks than ours. To my knowledge they have never been pruned.
If you just want to speculate or take an educated guess, that would be fine with me. I think my next step would be to start replacing them with a hardier tree one by one. It was not my choice in the first place but I am trying to make the best of an existing situation. If there are any chemicals you could recommend that would be helpful even if it meant it might be terminal to the tree if not successful.