I had a crest duck that is about 6 weeks old and she has a growth under her crest. I have noticed this growth on her when she was about 1-2 weeks old. The growth has gotten bigger and it seems to be growing outwards. The growth is hard and is attached to her head. I do not have a picture of the growth on me but I can post one later. She eats and drinks just fine. However, she is a little wobbly more so than the others and is very clumsy, and trips. Her feet turns inwards towards each other sometimes when she walks. I give all of my ducks brewers yeast and I switch it up every other day with a mineral and electrolyte mix that has niacin in it. I give them unmediated organic Purina chicken feed. I drew a picture of what the growth looks like and I have it labeled below. If someone can help me, I would greatly appreciate it. The growth is located at the back of her head.