Lethargic then dead...

[vtslaim]

Heat exhaustion seems to be the consensus here. Thanks for all your interest and advice and thank you in advance for answering my Qs!

 

[azygous]

There are nine different strains of coccidia that target chickens. Just as with Marek's vaccine, it doesn't cover all strains but helps a chicken to develop resistance. Therefore, it's always possible for a vaccinated chicken to still get sick.

If you've been walking around another locale where the coccidia are of a different species than where you live, your chickens may not have resistance to coccdia you tracked home on your shoes or on machinery that have brought the foreign parasites to your locale. Warm, humid weather can cause a population explosion and increased the odds that your chickens could get sick.

You can get the sulfa drug here. https://pet-healthcare.revivalanimal.com/search?w=fish sulfa forte

 

[Criticalicious]

Tractor Supply usually carries Corid and Nutridrench in the meds section. Corid comes in a liquid and powder form. Mix it with the drinking water at the proper strength (lots of resources on here with the dosages). I would start with the Nutridrench because it's the easiest thing and see if that helps. You should see results quickly. If you see any indication of bloody diarrhea, that is usually coccidia and then use the Corid. Nutridrench is a vitamin supplement though and you don't want to give that while dosing Corid because Corid works by starving the coccidia of vitamins.

The potential of bacterial infection from anaerobic bacteria is an interesting one. If the deep litter isn't being turned enough, that's when anaerobic bacteria can develop.