3 month old pullets sneezing, coughing and now bloody poop. Help?

I purchased two pullets from a lady who had a lot of very health-looking beautiful chickens in her back yard. The yard had been very muddy lately, she admitted, but it looked better when I got there. One of the pullets, a Rhode Island Red, had been sneezing occasionally when I got her, but I didn' think much of it. When I got them home, they both started doing it incessantly and it began to sound rattly and wet, with clear drainage from their nose. They were eating and drinking well though and seemed to have plenty of energy. Their poops looked normal the first day, but the second day began to have blood-tinged mucousy material in it.

I kept them separate from the other chickens and started putting goldenseal tincture in their water and shot an email over to the lady who sold them to me, asking if any of her other chickens at her place have these symptoms. She said no, but that she sometimes treats with terramycin if this kind of thing happens. I'm not a fan of antibiotics, so I'm looking for other ways to treat this.

Does anyone know what this is and what can be done?

Here's a picture of the pretty girls:


The girl in the forefront is obviously the Rhode Island Red, and the other is an Olive-Egger (Blue Ameraucana crossed with a Marans).

I really appreciate any suggestions.

 

Does this sound like cocci? I do have the medicated feed for them. They are not vaccinated.

 

Thanks for the help! I'm having trouble finding Corid online in a size for chickens, and when I did find it, it's not from a place where I can get fast delivery. Any suggestions? I'm in the Seattle area.

Thanks!