Coryza Advise Please

I've done my research and determined that I've got coryza in my flock. 2 of 16 showing severe eye swelling & bubbling. 2 others wheezing & sneezing.
Getting my list together to go to the store & pickup tylan 50.
I made a big mistake by purchasing 5 new birds & not keeping them isolated, I wrongly trusted the source because I'd gotten a bird from him a couple months prior who was perfectly healthy. Anyway. A few days after bringing the new 4 pullets, 1 hen home, notice both cochins, a pullet & the hen are sneezy & wheezy. The gentleman was selling all of his stock because his hours had changed at work (police officer) & he didn't have the time to care for such a diverse farm anymore. I chalked the cochins sneezing & wheezing up to the fact that his barn had gotten a bit under par since my last visit, the fumes were getting strong & the Cochin's don't roost up out of it like the lighter breed other 3 I'd gotten.
Unfortunately I took no action then, about two weeks ago and now two of my original girls have horribly swollen & bubbling eyes. Just one eye on each bird.
Obviously I'd want to treat my two with they eye problems, and the two with breathing problems, but I'm thinking I should treat my whole flock.
The worry is giving antibiotics to a healthy bird, but I seriously do not want to battle this for months because they're passing it around!
I know all of my full sized birds will get 1/2 cc orally once a day for at least 7 days.
A couple of they younger pullets (that aren't showing symptoms) are about bantum hen size, they'd get 1/4 cc.
BUT, I've got two 9 week old chicks.. No symptoms, but definitely exposed, if I treat them, they're about half the size of the youngest pullets, so 1/8cc??
Another question. The oral syringes. If I've got birds that clearly have it, and birds that show no signs, if I am to treat them all, I wouldn't want to infect them with the syringe.. So do I need a new syringe for each treatment of each bird?! Or at least one for each bird, sterilized between doses?

This is my first illness & I'm hoping for my girls sake I can do this right!

There's probably a 6 week timeframe to throw out eggs? Only one bird (original, with eye swelling) that is laying, along with 3 others with no symptoms. I dont see any reason not to feed their eggs back to them while they're still getting the treatment, but after the tylan course is over it seems like that would prolong the antibiotic in their system.
Let's see what y'all think.
Thanks so much, these girls (and boy) are beloved pets & my favorite hobby!

Update.. Maybe its not coryza but just a nasty uri.
Anyone have any surefire way to tell the difference.
They do not stink, even the bird with the worst swollen eye. No foul smell from their faces.
The inside of their mouths are clean.
Thoughts anyone?

If they were mine and I thought that they had mycoplasma and I wanted to use Tylan 50 I would give 25 mg per pound orally twice a day. The 25 mg per pound dose is 0.5 ml (1/2 cc). Of course I would treat only birds with symptoms.

From the mfg of Tylan... it's for for the powder, but pretty sure it's a better choice that giving 1/2cc once a day.
Quote:

CRD indications:

• Administer medicated drinking water for three days; however, medicated water may be administered for one to five days depending upon severity of infection. Treated chickens must consume enough medicated water to provide 50 mg per pound of body weight per day. Only medicated water should be available to the birds.

Turkeys:

• Administer medicated drinking water for three days; however, medicated water may be administered for two to five days depending upon severity of infection. Treated turkeys must consume enough medicated water to provide 60 mg per pound of body weight per day. Only medicated water should be available to the birds.

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-Kathy