It's mixed loosely, they frequently pick out just the feed, or just the grit or just the oyster shells, because I can see it scattered on the ground if they choose to not eat it.
The grit is adult sized and is combined with the oyster shells and both are mixed in with the feed when I give it to them. They are also allowed to free range in the yard, so they get additional grit from that.
It's possible the Ameraucana wasn't getting enough grit while isolated, but I'm not...
1) What type of bird , age and weight (does the chicken seem or feel lighter or thinner than the others.
Ameraucana hen, 1 year and 4 months old. She seems slightly thinner than usual, but is not emaciated.
2) What is the behavior, exactly.
General appearance of feeling unwell, unusual colored...