Are both sides getting the same amount of sun? Pachysandra will struggle if sited in full sun.  It prefers afternoon shade.  Also, it's not a good idea to mulch in between the plants.  This prevents them from spreading into a continuous ground cover.

Were the new plants being checked regularly for watering needs? Could they be under-watered or over-watered (is there an irrigation system in those beds)? Last year was quite dry overall.

Soil testing will not diagnose any infection or issue aside from nutrient levels, or an improper pH level. Fungicide spraying is not always a reliable way to keep the blight at bay. A better use of the funds would be to install a mix of other site-suitable groundcover species instead of more Pachysandra, that seems to be determined not to grow there.

Some suggestions for evergreen groundcovers that tolerate sun are:
Creeping juniper (Juniperus horizontalis) - low growing conifers with branches that spread over the ground.

Sedge (Carex ssp) - grass-like plants, each clump will spread to cover the ground.  Many different varieties, native and not.

Creeping thyme (Thymus serpyllum) - mat-forming, drought tolerent once established, likes full sun and poor soil and produces lovely small purple or pink flowers that attract polinators in the summer.

More on groundcovers from U of Md Extension.
https://extension.umd.edu/resource/groundcovers/

Hope this helps.  Thanks for contacting Ask Extension.