.....One of them has developed a croupy sound.  I would puchase Poultry Rx and treat either the 1 chicken with the cough or the entire flock. Depending on how long she's been having the cough, I would rather treat the entire flock.

Has anyone else had this problem?  This could be from a change in the weather or season. It could be that she is getting sick or is allergic to the bedding. My bet is that she is getting sick and I would treat her with Poultry Rx

I've also read where people worm their chickens.  How do you go about doing that, why and how often should this be done?...you can either worm them with Pig Swig which is a wormer for the water. There are other like Pig Swig which you can treat chickens. Just read the directions and since they are either about to lay or have already started to lay don't eat their eggs unless you are over the withdrawal time. Some use pumpkin seeds or garlic cloves in their water to natural treat your chickens. Verm-x ( I think is the name..check through the chicken section of the forum) has no withdrawl on your eggs.

Some worm when the flock is molting because the egg production is low due to the new feathers coming in.

Some worm because their egg production is low and then they get a high # of eggs that can 't be eaten.

Some worm on a yearly bases to just to the flock healthy. We worm right as winter comes into spring and when we introduce the replacement pullets to the flock.