Some of the limbs are turning black and the trees are weeping sap.
Peach Trees Not Doing Well
Certified GKH Gardening Expert
The blackening could be from sooty mold, which is often brought about from pests. In this case, the pests could be peach borers or aphids. Neem oil can help with both the sooty mold and aphid or other pest problem. The article on peach borers will help if that is the problem. Here is more information: