6/14 hatching keep finding dying chicks

1) What type of bird , age and weight. -
6/14 hatching they are small - variety pack of pullets, australops, red stars, speckleds, barred rocks, and I think leghorns or some kind of yellow chick
2) What is the behavior, exactly.
They act fine and I will run across a chick who is extrememly sleepy and is on their side
3) How long has the bird been exhibiting symptoms?
Very quickly they all seem fine one minute and I check on them and someone is acting sleepy not eating or drinking
4) Is there any bleeding, injury, broken bones or other sign of trauma.:
No
5) What happened, if anything that you know of, that may have caused the situation.
They had a rough delivery from the P.O. due to a mix up exposed to heat and no water source on 4th day
6) What has the bird been eating and drinking, if at all.
When I find a sick chick I administer water immediately with a spoon to get them to drink a little every half hour or so
7) How does the poop look? Normal? Bloody? Runny? etc.
I am not seeing any runny or bloody poop at all
8) What has been the treatment you have administered so far?
I added ACV to their main water tank and I got them all to take some plain yogurt. At this point I just want to keep the rest from getting sick. I have also lowered the brooder temp - it is about 85 degrees. None are acting cold or bunching up. I am wondering if the heat was making them sick.
9 ) What is your intent as far as treatment? For example, do you want to treat completely yourself, or do you need help in stabilizing the bird til you can get to a vet?
The sick chicks die within a few hours - their breathing slows they keep their eyes closed and I just keep them warm and the are less and less willing to get liquid. Meanwhile the others seem fine until I find another sick chick.
10) If you have a picture of the wound or condition, please post it. It may help.
None to see unless you want a pic of the dead chicks
11) Describe the housing/bedding in use
Clean play sand - never had a problem with it.

Feeding them purena med chick starter, water, now adding ACV and plain yogurt.


I posted earlier and I cannot find my original post but I didn't use the formated questions
Caroline