They might not be getting enough sun. They pretty much require 6 hours. If you can move it to where it gets more sun it would do better. I have monkshood and its one of my favorites

You know, with a shade garden with 2 hours of bright sun at midday, it's interesting how many plants you can actually get to grow fairly well (OK, maybe not flourish...but shade gardeners can't be that picky, can they). I never would've thought that Asiatic/Oriental lilies would do well in a shade garden, but I've been following a thread that says they do fine. Go figure! That said, I'm hoping my monkshood can be happy without 6 hours of sun...it is SUCH a wonderful looking plant/flower. It's too bad more people don't grow it (in spite of its poisonous nature).

I love my monkshood.I love the leaves, the way they shine like someone came along and polished them. I won a blue ribbon at the flower show with my exhibit of the bloom. Mine probably get 5 hours of sun. I also have some planted in the shade and I noticed the bottom leaves get yellow.
Asatic lillies are listed as plants that do well in the shade.

You know I have had a monkshood in my shade garden for a year now. This garden is in front of two big trees and gets no direct sun. I would say that the monkshood is about 2-3 ft tall and doing really good. The funny thing is I tried to start 2 small new ones right next to it over these past few weeks and they turned yellow. I cut them down to the ground and after reading this post think I will try to move them out so they can get more sun. Anyway I just thought it was funny how the one is thriving and the other two didnt.

Interesting post about the asiatic lilies doing well in shade. I just may have to give that a try!