I have taken Advanced Burn Life Support and Medical Management of Chemical and Biological Casualties through the military. I will apply those principles the best I can given the limited knowledge of the situation.
1. You're chickens are suffering smoke inhalation injuries. They are not suffering infection currently, but are suffering from inflammatory responses in relation to the damaged tissues. The result is the same as the body fighting infection though-fluid pulled into the area by bodily mediators.
2. They will be working to cough up/sneeze out and expel the damaged tissue. If I read correctly we are 3 days out now? Fortunately, human burn/severe inhalant injuries are immediately intubated for fear of loss of airway related to item one-inflammatory response, swelling, closing. Not saying they are completely out of the woods, but if it is 3 days now, then inflammatory response hopefully will not be any worse than it is currently meaning their airways remain intact. Also, being three days out means any carbon monoxide will have been processed out at this point (after a day that would cease to be a concern).
3. Supportive care. It is all you can do at this point. We can't throw these guys in a little ICU like we can people. However, in terms of air management you want to provide cool air mist humidifiers. Cool to sooth, moist to keep airways from becoming more irritated. Also, dry airways cannot mobilize the damaged tissue to cough out and expel. Ever wake up on an extremely dry and cold morning and have cement boogers in your nose? It is the same concept. Mustard/chlorine gas inhalant injuries can really only be treated with albuterol to open the airways and increased oxygenation-open the opens to get the crap out and deliver as much oxygen as possible. If you have an oxygen tent, go for it, they may learn they feel slightly better with increased oxygen and dwell their.
4. If they make it 1-2 weeks begin monitoring for upper and lower respiratory infections at that time. Rounds of antibiotics may be called for.
5. Knowing when to quit: if complete malaise takes over and they cannot get up any longer or just lie their panting in some strange posture, it will probably be best to end suffering at that time.
Best of luck with everything and good job getting them all together and tended to. The eating and drinking is always a good sign.