If these boxwoods were in the garden during spring (either pre-transplant or post), their symptoms are consistent with cold damage on the youngest growth. We have seen a number of cases of damage on vulnerable foliage due to the multiple late-season freezes/frosts we experienced. Nothing can be done except to selectively trim out the worst of the damage (if need be, as an eyesore) and wait for subsequent new growth to cover it up.

If the damage has only appeared recently (after mid-May), and the plants were transplanted not long before these symptoms, this could be minor leaf burn from root damage. Transplanting does damage and remove some fine roots, despite when done carefully, and this can cause the most vulnerable tissues to desiccate from lack of sufficient water. As the roots regrow, they will better be able to keep all of the leaves hydrated. Here too, the damage can be removed or will be covered-up in time.

While this does not match symptoms of common boxwood pests or diseases, you can keep an eye on them going forward. Here is a page on various issues that can arise with boxwood, though some varieties are much more susceptible than others: https://extension.umd.edu/hgic/topics/boxwood-preventing-and-managing-common-pests-and-diseases

Miri