What's Wrong with these Plum Grafts?

I have two separate Kirke’s Blue plum grafts that look terrible. Right next to them (6" away on the same limb) I have extremely healthy looking Rose Marie grafts. One limb over, I have a very healthy Castleton graft. Maybe there was something wrong with the Kirke’s Blue grafts? The leaves are very yellow and sick looking.

Here are some pics:

Kirke’s Blue on left Rose Marie on right:

Castleton right next to it looks great:

Everything on this tree looks great except the Kirke’s Blue grafts…

Any ideas?