I received a very beautiful white hellebore full of blooms for Christmas and, in 2 weeks, the leaves all turned yellow. It still has new flower buds coming and a few small green leaves.
Certified GKH Gardening Expert
Yellowing of leaves can be brought about be a number of things, most often attributed to stress of some kind. This article should help in determining the cause for yours: https://www.gardeningknowhow.com/plant-problems/environmental/plant-leaves-turn-yellow.htm