in your case George as you don't race and only keep prisoner stock I would say its a easy game to keep them healthy and if one went off it could be seen as a weakness but for a racing loft their are so many more possibilities as they can pick up disease in the basket I have treated birds and they have been healthy from that day to this with no other illness or any other medication I would not advocate regular use with meds but they can be a help ...obviously some birds have stronger immune systems than others but that's the same with any species I suppose a bird with a brain and good immunity are the most desirable...but I don't see birds standing out in their condition they all look pretty well anyway ...