You can put a mulch round them after they get a good soaking @Big Blue Sky- some decent compost will do. They do like a moister soil generally, but with good drainage. Once established, they can cope with more fluctuation in conditions, but they don't really like poor, sandier soils. They will have suffered quite a bit from last year's conditions, and even plants which love sun and light soil need a lot of watering in those conditions while they establish.Stress due to lack of water is more common than stress due to overwatering. Airflow is important too, as @Borderline says. Pests and diseases on box love tightly packed plants.