Three diseased weeping cherry trees. Each has developed ugly black splotches...
The survival of your cherry tree is problematic. Your photo shows a significant canker which could be the result of a mechanical wound. The tree appears to be planted too deeply, which is also a stress factor. The vascular system of the tree has suffered at least 50% disruption, perhaps more. There is no reversal of the damage already showing. You should consider making plans for removal and replacement of the tree.
If all three trees are displaying similar wounds, the cause is most likely cultural, i.e., poor planting technique or mechanical damage, possibly done by a weed whacker or lawn mower.