i noticed about 1 month ago a barred rock hen wondering not herself all alone she ate and drank so i thought nothing of it. then one of my wyandotts was gasping for air. at the same time my rooster sounded like he had laryngitis he could crow very well. so within an hour that wyandotte died of gasping for air tragically and i realized this rooster must have the same so i brought him in to treat for worms with safeguard goat and put him on tetracycline. in the middle of treating all the other birds for worms i was picking them up and noticed the one that was wondering was extremely swollen like a balloon ready to burst. i also noticed there were two others like that also. so i brought her in checked her for a stuck egg soaked her multiple times no egg and no difference. there were three of them together then i noticed a tiny lash egg not sure who it came from. didn't find anything that helped so i put her back outside unfortunately it only got worse and about 2 weeks later , yesterday she died. so today i went outside and noticed a different one is swollen also so now i have 2 for sure and maybe more. i was unsuccessful with the first and would like to be able to help them. when i check the vent it is the same thing. very swollen inside almost no room for finger. i just went and got calcium gluco and gave them 1.5cc orally . was thinking about giving tylan shots but not sure it would be worth it. so i ordered baytril for parrots to give orally when it arrives. why do i have so many hens going through this they are all older 3-5 years, stopped laying eggs , free range so i dont check to see who laid eggs for the day. cant stand to loose any more birds. is there anything i can do. and how can i prevent this?