Maybe try giving them some protein too? If they are ex battery then it might take them longer to get better because of overall health too. Poor girls. Maybe see if your son wants to help with the birds and use it as a bonding activity for all of you? My kids love interacting with the birds.
I had an issue with gleet this spring. We treated with otc athlete's foot cream rubbed over the vent every other day, on opposite days I rubbed on blue hen healer, and added appke cider vinegar, honey, and cranberry juice to the waterer. I have no idea which one helped or if it was a combo of...