When is a good age, to put diatomaceous earth on the chickens? And would you use it like a light powder on them? It's food grade that I have so it won't hurt them right? I have two six week olds, one three month old, and a four month old. All silkies. Right now they are all inside but they are doing some scratching and head shaking sometimes. I wonder when the best time to apply the DE is? Thanks for you're help!