Old Rooster Acting Tired, Face Hot EMERGENCY!!!

[The Chickens' Maid]

Our five-year old BO rooster is acting extremely lethargic, to the point of just falling asleep. His face is hot and swollen with some sort of clear fluid. He doesn't want to open his eyes. His breath stinks, it smells like infection. He doesn't want to open his beak to far, either, but I don't know if that is because he is tired or if it is another symptom. We had another chicken (a five-year old Barred Rock hen) die six days ago (on the tenth). She was fine the evening before and even had to be herded in with the others. I found her in the morning; she seemed to have fallen asleep in the corner. Her head was tucked into her wing and her legs were straight out behind her, like she had just fallen over and fallen asleep.
We have had no inkling of disease before that, none of the other chickens are displaying anything.
I got the rooster to drink a little water. I am very worried about this spreading to the rest of the flock.
We have an antibiotic for a horse that we could give him. It's called tetracycline. I don't know what the dosage would be, though.
Can anybody help? I don't even know what this disease/infection is!
Thanks!

ETA: This was all very fast. I just found him like this when I opened them up this morning.

 

[RoosterRidge]

I hope someone comments soon that can help you out...

 

[The Chickens' Maid]

He's doing much better today! We called a vet, and she said to give him tetracycline concentrated for chickens. We gave him that, and he perked up so that he was standing and hungry. Now, after a good night's sleep, he is crowing and very awake, although he is still a little unsteady and not out of the woods yet. We are medicating the rest of the flock with tetracycline. The vet said that this was a bacterial infection that could have been related to the hen who died. We haven't had any other sick chickens so far, and I'm hoping that this will stop any infection before there are any other cases.