Chicks with some form of respiratory ailment, possible Coryza

[grumpycupcake]

My eight 2-3 week old chicks are all sneezy, breathing through their mouths when they sleep. I suspected respiratory irritation but one of the chicks has had very yellow snot that was at first clear and now a thick yellow which I’ve been cleaning off with a damp cloth. today it started to smell, so i separated him. There are 4 bantam breeds (old english) and 4 larger breeds that are mixed. Theyve been playing and eating like normal, except for the occasional lethargy for a few

Ive been researching like hell and I have no access to veterinary care in my area.
What can I do? I have a suspicion it is Coryza but I have no clue what antibiotics to use. I’ve ordered VetRX that comes in tomorrow but other than that I still need to buy things such as garlic and apple cider vinegar as I read it’ll help.

What do I do? I hate seeing them this way and i fear for the worst.

 

[grumpycupcake]

Let it also be known that the 4 larger breeds were what introduced this sneezing; my father got them from a coworker who is hatching many chicks on their farm.