Tonight one of my babies let me hold "her" and fell asleep in my hand while I rubbed her. Then all the others fell asleep too so it got really quiet. I kept hearing a sound that reminded me of rice crispy cereal crackling. Turns out it was coming from her. And then I listened closer to the brooder and I could hear that they were all making the same sound. I assumed that it was the grit that I had just given them grinding against one another in their crop. But after searching the forums here others seem to believe it is respiratory and didn't come to the same conclusion that I did. Should I be worried? They all seem perfectly fine. BTW.....I have them on medicated chick starter and only gave them the chick grit because they ate some pine shavings yesterday. I gave it to them in my hand and they all ate it like it was the best thing in the world to them. Maybe they ate too much?