My husband purchased 2 lemon orpington pullets at an auction and we had them for about 10 weeks now. They are lovely healthy birds and one has grown very attached to me.
I bought a black orpington hen about 1 week ago at an auction and she seemed fine at the auction house and did not show any signs of illness. Immediately when she was travelling in a box on our way home, she made noises like she was barking while in the carrier box. We did not think too much about it and thought that she was just a very vocal chicken who does not like travelling. She joined the flock that night. 5 days later, the 2 lemon orpingtons started sneezing and so did one of the 2 Lohmanns. The black orpington is still making the noise which by now I realise it is the sound of her sneezing.
I am trying colloidal silver on all the birds and especially on the lemon orpingtons and hope that they will get better soon. The lemon orpingtons were quite poorly yesterday. The heavy rain from the day before did not help as they were thoroughly drenched from the downpour. Both of the lemon orpingtons jumped onto my lap for a cuddle as they wanted me to comfort them. One of the Lohmanns also sat next to me on the grass for a cuddle. I hope they will all get better soon. They appear to be a bit better today when I put them to bed a while ago although they were still sneezing. The rest of the flock appears not to be affected by this sneezing though (which I find it rather strange).
From this experience, I can never again trust all sellers at auctions to put healthy birds up for sale. You might just purchase a bird that is carrying a disease and bring it home to your flock. Therefore, buyer beware.
Your birds have what is known as Chronic Respiratory Disease or a Mycoplasma Gallisepticum infection. It's a chronic infection that even antibiotic won't cure but will treat secondary infections which are causing the cold like symptoms you see it's highly infectious and will infect the other birds it comes into contact with. Even when the symptoms have gone the bird will still be a carrier and it will break out again under stress conditions. In fact it is sometimes call a stress disease and the stress of the journey home will almost certainly be the cause of the outbreak from it's dormant state.
If after an antibiotic treatment with Tylan or Baytril the birds have still got rattlely breathing it would be best to dispatch them as they will almost certainly have frequent recurrances. You should not breed from these birds or move them to another site or mix them with healthy stock. They may well also be poor layers and produce soft eggs.
I'm affraid your trip to the auction will have longterm consequences and incur expensive vet bills periodically. Colloidal Silver will have no effect whatsoever on this infection and in fact is a highly dubious treatment for any condition taken internally. I've never heard of it being used to treat chickens so I doubt a safe dosage, if such exists, is even known. A vet is the only person who is allowed to prescribe the antibiotic medication which your birds need so I suggest you pay him or her a visit pronto.
This story is a salutary warning to anyone introducing new birds they aren't sure of the background of and a warning to always quarentine new birds.
Best of luck
HF