Looks to me as if they were affected by cold weather. They look as if they might have been under cover before you bought them and not hardened off properly before planting out. I would give them aliitle longer to see if they shoot from low down, or dig one up and take it back to the supplier and complain/ask their advice!

Also, check the leaves, are there any black/brown blotches? are the underside of the leaves effected/ check the stems, are they healthy? these could be signs of boxblight, someone recently brought alot of small box for a knot garden, healthy when purchased then suddenly went brown, due to boxblight.julien.

I had three healthy box cuttings in one pot kept in the conservatory over the winter. I potted them on into separate pots and one of the has gone like your photo while the other two are OK. They were all treated alike, so I too would be interested in the answer!

I think you may want to investigate the boxblight theory as it seems to be coming more common! Hope its just frost tho and they recover!!Good Luck with them.

Thanks everyone. I am hoping frost damage !