Q.care for older neglected peach trees
I inherited land with 4 peach trees. The original trees have long since died and suckers have grown up some as large as 3-4 inch diameter. Last year I severely pruned and cleaned out dead wood to try to salvage them. I left a few upright suckers on each to see what might produce. One tree put on a lot of fruit. Another tree seemed to just grow more branches. One barely put on leaves and has maybe 10 peaches. What happened to get such different results? Do you think there is hope to get these to be healthy trees or are they too far gone?
One of the trees fruit is covered with little black dots like freckles. What is this and what can I do about it?

If the main trees have died and they are growing from a grafted root stock, it is nearly impossible to tell the type of tree that could be growing from the shoots.
Here are some links for you with more information.
https://www.gardeningknowhow.com/edible/fruits/peach/peach-tree-care.htm
https://www.gardeningknowhow.com/ornamental/trees/tgen/tree-sucker-removal-and-tree-sucker-control.htm
https://www.gardeningknowhow.com/edible/fruits/peach/tree-with-no-peaches.htm
https://www.gardeningknowhow.com/edible/fruits/peach/fertilizing-peach-trees.htm