Best antibiotic for respiratory issues?

[Scarletpyxi]

What is the dosage for Tylamox?

 

[BurtonsBirds]

HOw can you tell its pneumonia? that is what I think 2 of my chickens have had. One passed 2 months ago, the rooster is symptomatic now. Crown turning purple, and he sounds "wet" if he does get any sound out. What are the most common triggers for poultry pneumonia? Best treatment? Please help. Thanks so much!