13 month hen suddenly sneezing constantly and moaning

[big mami]

Hi,
I was down to one hen, then 6 days ago introduced 2 new pullets. Yesterday my original hen started sneezing and now it's nearly constant. No discharge, no watery eyes, funny moaning sound but not with every breath. Acting otherwise healthy. Isolated her in the broody cage last night. She is drinking water, might be eating, but not sure. I'm fairly new to chickens (started in September) so I don't know about remedies or where to buy them. I have read some posts on the subject, but am not sure if I should try to track down vitamins, VetRx, antibiotics for her water, or what. If my new ones gave something to my older one, should I treat the new ones also? They have no symptoms.

 

[big mami]

Now she is doing that strange moaning sound with every breath. She won't eat pellets or oatmeal. She is resting some, and scratching around the yard some. And it turns out the two pullets have clear discharge from their noses that I hadn't noticed. They are still acting normally. I put 1 tsp Aureomycin and 1 tsp GQF-Vitamins Plus in their water and put VetRx in the sicker one's nose and mouth. Can I put the sicker one back with the others since they all have it? The coop is a little warmer at night, and she would be more comfortable there than in the broody cage.