I'm going back to answer questions:
They haven't had grit, are in a coop/pen and the ground is frozen with snow. I haven't shoveled out the run but have put hay on top of snow so they'll come out. They've had no opportunity to find grit unless they've been able to scratch frozen dirt.
Mites vs frostbite: when the sun comes up, I'll see if the black dots are still there. I've read that mites hide during the daylight hours but come out at night to feed on the poor chickens. If it's frostbite, it should still be there.
I see no evidence that any other animal has been in the coop. That is highly doubtful as their coop is pretty tight and hasn't a dirt floor.
I'm feeding a commercial feed that is 15% protein. I don't give any scratch. I do give occasional raw ground liver, fresh (unpasturized) milk that has curdled or yogurt, if I have it, assorted greens and kitchen scraps (I use only organic foods and prepare everything from scratch so they are getting nothing junky)
I felt up and down one of the girls necks yesterday and nothing like a full crop. I've never felt a full crop but I expected it to be like a hamsters cheeks packed full... sorta? My husband felt nothing of the sort in our dead chickens neck, either.
If we need grit or not, it's now in there... a pile of it under the feeder.
I'm going to make a bowl of high protein feed for them before I go to work... thanks for the recipe. I'll use some of that raw liver ground up finely, though, with some honey, some bentonite clay (worming purposes), the curdled milk, and some oats soaked.
I did buy some powdered vitamin/mineral/electrolytes from Fleet Farm last night to add to their water, as an extra boost since they do look debilitated.
I've always added cider vinegar to their water since the day they arrived as tiny chicks. I thought that was supposed to help with overall health and worms, etc.
My husband says "that's what you get when you go all organic and don't get medicated feed etc etc etc" Is that true? They have been vibrantly healthy, fat and shiny beautiful up until just a few weeks back. It seems to correlate closer to the change in this much coarser feed than anything... although I can't rule out worms at this point. Or mites. But mites apparently won't kill them this quickly, right.
They are noticeably thinner. So something is interfering with their nutritional intake/conversion. No grit or worms?
I'm going out shortly to check on them. I pray there isn't another dead one.