I've had a group of white unnamed hellebores growing for almost 20 years. The last few years, they haven't appeared to be growing as robustly as they once did. I had a few flowers last year but none this year. They are growing at the base of a barberry shrub and have been for years. I don't generally fertilize my perennials and I've started mulching last year with shredded fall leaves. Should I consider moving the hellebores? If so, when would be a good time to move them?