I am looking for a good food that is grain free and would help build the immune system. I have 5 dogs total and two are fosters from the local shelter. Those two have demodectic mange and are on daily doses of ivermectin. I am currently using Taste of the Wild High Prairie. The mange is showing little progress and I have had them for a few months. I did discontinue the ivermectin for a period but am back giving it to them. I am also sprinkinling a human probiotic in their food. Is there anything more i can do?