Hmmm...
An iron deficiency would not show up that quickly.
I am with Mike on the shock factor.
Pretty hot to be moving trees.
A nursery grown tree becomes accustomed to a certain 'water table' and when it is moved to its new home does not have the same conditions it was used to.
Potted plants become used to sending roots downwards (and around) because of the way they are forced to search for water and nutrients.
When they are placed in their new homes they are still looking for that regular watering/feeding cycle.
They are usually disappointed in this because the the new owner does not water deeply or regularly enough.
It can take several years (depending on the age/diameter of the trunk) for the tree to become established in its new location.
You also have to consider the whole clay soil thingy.
A lot of these trees you get are used to a porous type potting mixture.
Then you put them into a heavy clay soil environment and they just don't know what to do.
Water puddles up in the hole.
They send their little roots out, and can't find an opening in that hard packed clay.
What I like to do is, dig my planting hole really wide.
More so than deep.
I don't amend much with compost or anything.
I just want the soil loosened up so the new roots can crawl through easily.
I make several really deep cuts (inch or more) around the root ball and a couple on the bottom.
I've even been known to wash all the dirt out of the root ball at times, but I don't always do that.
The thing about watering in clay is; you want to water enough to keep the baby alive, but not enough to rot the roots, and make it send out new ones into the surrounding soil.
A lot of people I have seen, just water right up close to the tree.
Roots are like puppies; they will seek that nipple out.
They will crawl all around looking for that nipple.
Water the whole area and they will move right in.
On a side note about walnut trees. They pretty much don't like anything growing around them. The husks of the nut themselves, make a pretty good fishing lure also.