If @casportpony is available she might be able to help. She's pretty good.
I'm not sure what is going on. I'm not familiar with Quik Chick, I assume you are feeding it in the recommended dosage and replacing it daily so it doesn't get stale. As long as you are not overdoing it then it should not be doing any harm. Some of those boosters are supposedly only for their first water but it looks like Quik Chick is OK to repeat.
I'd call the hatchery and talk to them about this just to cover all bases. If this is happening to other customers they may have heard about it.
I'd stop the grit. It's unlikely it is contaminated but remove one variable. If all they are eating is chick feed they don't need grit.
I can't see that you are doing anything wrong at all. Hatcheries are generally really good at biosecurity and isolated in that bedroom they should not be exposed to any diseases. That brooder does not look wet which removes one concern. I don't know of any poisoning that would slowly kill a few at a time like that, especially since you are not feeding any other treats. There should not be any fumes in that bedroom.
I'm at a loss. Mainly because I don't know what is going on I'd clean out everything. Take the partition down so they have the entire area. Get rid of the newspaper and maybe get a bag of pine shavings to use as bedding. Try washing the waterer and food dish (rinse them well) and try fresh water and maybe even get a different bag of feed. Something is wrong and I don't know what it is.
I'm not sure what is going on. I'm not familiar with Quik Chick, I assume you are feeding it in the recommended dosage and replacing it daily so it doesn't get stale. As long as you are not overdoing it then it should not be doing any harm. Some of those boosters are supposedly only for their first water but it looks like Quik Chick is OK to repeat.
I'd call the hatchery and talk to them about this just to cover all bases. If this is happening to other customers they may have heard about it.
I'd stop the grit. It's unlikely it is contaminated but remove one variable. If all they are eating is chick feed they don't need grit.
I can't see that you are doing anything wrong at all. Hatcheries are generally really good at biosecurity and isolated in that bedroom they should not be exposed to any diseases. That brooder does not look wet which removes one concern. I don't know of any poisoning that would slowly kill a few at a time like that, especially since you are not feeding any other treats. There should not be any fumes in that bedroom.
I'm at a loss. Mainly because I don't know what is going on I'd clean out everything. Take the partition down so they have the entire area. Get rid of the newspaper and maybe get a bag of pine shavings to use as bedding. Try washing the waterer and food dish (rinse them well) and try fresh water and maybe even get a different bag of feed. Something is wrong and I don't know what it is.