When a young tree dies and sprouts come up from the root stock, there is a huge problem.
I just read that you bury your trees up to within inches of the graft. This might be your entire problem.
The root stock has a trunk with bark that belongs out of soil, mulch, weeds...any thing that might hold moisture against the bark of the trunk. Above the graft, the tree still needs a vascular system free and clear of disease, rot, bacteria. Protect the bottom of your trees below that graft from being girdled or you will lose your trees.
When a tree is planted it should be in a hole the size of the root ball...a little wider but not deeper. The soil below the rootball needs to be UNDISTURBED soil. It sounds as if you are good for depth but what is this cow manure, chicken innards you are adding? Sorry but adding non decomposed organic matter is going to rob what little nitrogen that may be in the compost from use by your tree roots. Have you ever composted? Remember they always say, "no meat products, cat poo, dog poo should be added to your compost"? Plants make their own food as long as they have a little nitrogen, phosphorus, potassium and 12 different micro chemicals, regular but never too much water, great light, your trees should thrive. In Zone 6? Absolutely.
Forget about the trunk cover for the deer. They will eat the leaves and if really a problem you will put a cheapo wire fence around it, a couple of feet away from the tree. I would also buy a bale of hay now and then and dump it far from your trees and garden. They are there they will eat and to give them something cheap, simple will save your plants. Also, those motion sensor driven pulse sprinklers...are cool for all animals as a deterrent.
Do you have a dog around? Just the smell of dog will keep deer uninterested in your trees, plants.
The fact that you've had success with other types of fruit trees is telling me something might have been very wrong with the trees themselves. What species and variety were they? Did they come advertised as resistant to any disease? Did you plant these cherry trees differently than your apples, pears?
Need pictures and might have you do a little cutting to show a picture of the vascular system near the graft above and one below. You might have had a tender variety, susceptible to:
excerpt from article posted in full...
Cherry trees are far from hardy. Rather, the trees are relatively fragile in comparison to other species. Consequently, they are often targeted by diseases which can severely damage or kill them.
Some of the most common diseases that attack cherry trees are:
Black Knot: Black knot is a widespread and serious disease which
affects the tree's twigs, branches, and fruit. The fungus can also
cause abnormal bark growth and produce light-brown ulcers that rupture
as they mature. If the disease is ignored, the tree can die within a
couple of years.
Silver Leaf: This fungal disease leaves a silver luster on the tree's leaves. Over time, the leaves will brown and toxins in the
fungus will attack the tree's inner vascular system causing it to die.
Powdery Mildew: This fungus makes its home on leaves and twigs. Symptoms include whit, powdery marks on new leaves. In severe cases
the tree's leaves will curl and drop prematurely.
Cherry Leaf Spot: The disease produces small dark spots on the leaves. In some cases the fungus spreads and causes the leaves to
yellow and drop. In other cases, white spores may form on the
undersides of leaves and spread to the tree's fruit.
To a lesser degree cherry trees are also affected by cankers. The
bacteria cause spots to form on the tree's leaves and lesions to form
on the fruit.
cherry trees and disease and etc
Please send pictures of your trees, close ups of leaves, close ups of trunk/soil connection. Who does the pruning? Do you sterilize your pruners between each tree/plant? Most do not but this is how most of our ornamentals get diseases...passed via pruners. Mower blades.
What have you done if you can remember, differently for the cherry trees from the other trees you've planted?