i don't know that you'll have to put your flock down. your swollen eye is now indicating you need to run and get one of those drugs. our chicken and many chickens go through this. just go to a feed store and get the antibiotic for like $5-10. you can call the manufacturer for help in how much to give. Erythromycin, tylosin, spectinomycin, and lincomycin.
TSC will have one of these...it might not be labeled for chickens but goats or something.
if caseous material (yellowish nasty cheese and a stench) starts appears in this eye, then coryza has set in too. they often come together. so you'll run back to
TSC and get the nfs puffer. it is made for dogs and cats and near the horse medicine. use gloves
an ointment for they eye, or a saline/epsom salt wash daily will help clear up the swollen and fizzy eye.
it is not that big of a deal. you'll save the $70 vet bill we spent.
if you don't treat this soon, crud will be deposited in the sinuses or nasal cavity. this will make the eye fizz for a long time. a vet may have to wash it out.