Why are leaves turning yellow on newly planted plants?
Certified GKH Gardening Expert
There is likely some transplant stress for the plants. The adjustment from greenhouse to outdoor lighting can cause some leaf yellowing.
Yellowing of leaves can also indicate watering issues. Too much or too little water.
Check the soil, your Hellebores need well draining soil. The new plants should have moist soil but not soggy.
Here is a link to refresh you on the care requirements.