Trees should never be planted any deeper than they were previously and not any shallower than they were previously. There should be a knot at the bottom of the tree where it was previously growing make sure that knot is flush with the ground. In other words if its a root ball always plant your tree flush with the ground.

With that said, most likely problems after a transplant is over or under watering. If the tree is planted correctly it may just be underwatered. Some take a 5 gallon bucket fill it with water make a hole at the bottom where water can leak out slowly, place it where the root ball is. Trees being transplanted love their water till they get adjusted and if your tree isnt in the ground enough then it is suffering from being to dry. If your root ball is to deep and your leaves are yellow then your tree is suffering from over water. The best way to water is slow and long directly on the rootball.

Yellow leaves = overwatered
Brown leaves = underwatered

I hope that helps ya!!

By 'transplanted', do you mean that you've removed them from one location and replanted them elsewhere? If so, what size are they?

I would expect many plants to look a little sickly three days after a transplant, especially woody perennials.

I have the same problem! transplanted 3 birches that I found growing
On top of a huge stump on a beach. No root ball. Brought them home with a fair amount of the roots still intact
And planted them. One had and still does have brown leaves but is still green. Another has brown and green leaves and has not changed.
the prize one which is about 8 feet tall did have green leaves now has all drooping brownish leaves. I have been watering. When I planted it I added
Some topsoil mixed with sand, compost and sphagnum moss.
I thought it was planted too deep so have uncovered most the top dressing to where the trunk meets the roots. Should I raise it to the ground level? Any ideas?