2 chickens are coughing, sneezing and one sounds raspy... PLEASE HELP!!!

Hi there..

I have two chickens that are couging,sneezing and one that sounds raspy. My hen started awhile back and I gave her tetroxy HCA 280 this didn't seem to help her or my rooster. My rooster is the one that sounds raspy. I have treated them with safeguard paste to make sure there were no gapeworms ( I gave a pea size, how often do I need to give this to them) I have seperated them from the rest of my flock. ( they seem to be doing very well) These two chickens aren't acting very sick... eating, drinking and my hen is laying... Any help would greatly be appreciated as my hen has been sneezing and coughing for about a month now, and my rooster just about a week.