That does not appear to be a normal sort of leaf scorch (if any scorch can be considered normal!!). It does look like some early signs of Pseudomonas. For whatever reason, JM's with brightly colored bark (any of the coral barks, 'Japanese Sunrise', 'Bihou', etc.) tend to be more prone to this pathogen than others with typical bark coloring.

Generally, this is something that is most evident in early spring as the tree is just starting to bud out and is characterized by blackened tip die back and the presence of blackened or black spotted leaves, usually beginning on the top of the tree and moving downward. Moist springs tend to encourage or accelerate the problem but I'd suspect summer humidity can also have an effect, if the bacterium is present. The recommended treatment is to prune off affected areas, going a good 3-6 inches behind where the symptoms are present. And be sure to disinfect the pruners between cuts!!

If these were my trees, I'd be inclined to leave them alone for this season and see what happens over winter. If possible, keep them in area that is somewhat protected in winter, out of any strong winds and with some cold protection. If you see signs of this happening again in spring as the trees begin to leaf out, do your pruning at this time.

FWIW, Bihou has been determined to be a rather weak cultivar of JM and prone to a number of issues, the pseudomonas being only one, to the point where some European growers no longer produce this selection. Hopefully, your trees will outgrow this current issue with care.

Bihou and some of the other coral bark cultivars are known for getting pretty messy-looking and prone to infection. Bihou is particularly weak. On the UBC page Tim Nichols mentions that the blackening of Bihou is most likely Alternaria, not Pseudomonas. Most of the JM collectors on that page have trouble with it, and a couple mention the leaf spots as something that returns every year.

Far be it from me to dispute the experts on the UBC forum but Alternaria seldom afflicts JM's and doesn't present in the same manner as the discoloration shown on the leaves in the attached photo. Neither does Phyllosticta, which is another very common JM leaf spot. Pseudomonas, however, IS known to be extremely prevalent on any of the coral/colored bark varieties. Alternaria can be disfiguring but pseudomonas also has the potential to be fatal, so given the choices, I'd treat for that (fungicides are appropriate for either affliction as would be dormant sprays but avoid spraying when leaves are present....best done during dormancy).

But I do agree that Bihou is just not a strong, robust selection. You will likely have ongoing issues with these plants.

Good to know. Thanks to you both, Pseudomonas were specifically mentioned by the wholeseller, I'm just a little surprised they'd still ship out affected specimens like that.