Went out to feed the ducks this morning and my female can't walk, she has no strength in her legs. She was totally fine yesterday, I let them in the yard during the day. She is about 7 months old, and has been laying (until this morning.) I got the ducks from ideal last summer, I bought 3 and lost one to a similar problem. I am feeding them 18% duck pellets, which I've been feeding for about a week now (before I was feeding chicken layer mash.) could this be the problem? Should I give her niacin? The male seems totally fine. Thanks!