The quality and reliability of nursery practices vary from one side of a town to the other let alone across oceans! But plant stock grown in pots can hide many defects that are easier to pick in bare rooted stock. Your trees sound very young, how many did you buy and plant, and are they all suffering the same symptoms?
Young trees are very resiliant and able to bounce back from most minor problems, however despite being virtually 100% active tissue unlike older trees they have only small reserves of energy to commit to cellular maintenance and defence, having to regrow the entire volume of foliage twice will have induce significant stress.
Without pics its very hard to give you precise answers, you would not expect to see brown streaking just under the thin outer bark on a young maple, but if you scratched too deeply you would break through the cambium and then yes you would see light brown colouring.
There's nothing lost by persisting with the trees for a few months yet, I wouldn't be ripping them out of the ground unless you are convinced they have died.
__________________ Sean  Trees are poems that earth writes upon the sky,
We fell them down and turn them into paper,
That we may record our emptiness.
- Kahlil Gibran
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