Ok, the ones that got too hot is not on the place you got them. The second group sounds like they were already sick when you got them. I'd contact them, and let them know, only about the sick ones from the second batch you bought. They may have had enough complaints that they're aware, and...
I do the Manna Pro chick grit too.
So, most of the chicks from the second batch you got, are the ones that have been ill, and a couple have died. Am I getting that right?
I love it the first time I put out a few mealworms. They all retreat, then slowly creep towards them. Eventually the bravest one or two of the bunch will approach them. Soon, one of them will take a quick peck. A moment later, one of the brave ones will grab one, and retreat back with the...
My temps were/are just fine. Large brooder, warm on one end, cooler on the other, 2 thermometers, so they could/can seek out whatever temp suited them. This happens with every hatch, and has been going on for years. When hatching my own, I've never had pasty butt, or lost one when brooding...
Something else I learned the first time I incubated, and put the chicks in the brooder.....They run around like crazy, then BLAM, down they go. It's like they run out of energy, and pass out. They're fine, and it's normal. Later they'll "revive" and be very busy for awhile, then Blam, down...
There are only 2 things you might want to change. Stop with the ACV with chicks. While ACV has benefits, it also has disadvantages, especially for chicks.. It's better suited for pullets a couple months old, not chicks. Instead, get some Nutri-Drench, and add about (1/4 dropper full) about...