Welcome to BYC. Can you contact a local vet today, and ask about getting him seen for a possible respiratory disease? Some feed stores sell Tylan 200, and it can be used, but the dosage is 1/4 that of the 50. Here is where you might be able to find Tylan powder for the water: https://www.nepigeonsupplies.com/product/tylosin-powder/
Dosage is 1 tsp per gallon or 1/4 tsp per quart of water for 3-5 days. Be sure to add the water to the powder, not the other way around to mix, and change it every 3 days.