It tastes good to humans but I read it has a coating that tastes bad to chickens unless washed. Not to argue or anything, just my opinion from
a Paleo-based nutrition on grains. Something about lectins I believe.
I have heard they can eat quinoa, but it has a nasty tasting coating around it. It isn't healthy for humans, so I can't imagine it being healthy for chickens either.
If it isn't mites, which it sounds like it isn't, or worms, try feeding excess calcium to help up their production. I had a similar problem ( and still do though it is getting better) with our 2 year old hens barely or not laying at all from spring until now, and it seems to be picking up. I am...