Don't just take my advice without checking it out with others, becuase I have only had one horse in my life and only had her for a little over a year.
My horse has bad feet from my being uneducated about hooves and not knowing what to look for etc. I am working hard to get her back to having functional hooves now. It is a long process.
Anyway, what I have found that works good as a thrush preventative type of thing, instead of the Dawn is a 50/50 mix of apple cider vinegar and water. I keep it in a spray bottle and after picking the feet I spray them with the vinegar mixture and so far it seems to be helping my horse allot. If there is a small area that I just can't get cleaned out all that well, I blast it with the spray bottle and it seems to work.
I have only been doing this for the last couple of weeks, but so far it is working for me and it doesn't seem to dry her feet out to much. I stay away from the iodine because it seemed to be to harsh for my horses feet. I tried Dawn soap as well but had problems also with rinsing and it dried her feet out.
I have, when the conditions have been really wet, used the medicated powder on her feet and legs as well and have not noticed a problem doing that.
This is just what has seemed to work for me so far in regards to thrush. But, like I said don't just go on what I say, check everything out for yourself and research, read, and learn all you can about feet. There are so many different opinions out there and different ways of doing things. You can't take anyones word for anything. You have to try to learn as much as you can. (that goes for vets too.)
As for the BO. Some people have a way of life where they feel if you don't state it is a problem it isn't. So, when my horse has anything wrong with her my BO always seems to be right there (20 ft away) telling me what ever it is I am concerned about is "nothing" and that my horse is "fine". So are hers when I let her know they are limping, laying down, not eating etc. It is just the way some people are and (not that it did) don't let it get to you and ignore it and don't place any value in their opinion.
When my horse did a flying summersault through a pipe corral gate, the advise I got from "people" at the barn were to "give her bute", "let her graze in pasture", and the ever popular "she'll be fine, she's not lame!" Had I listened to that advise instead of making an emergency call to the vet my horse would be dead. She was in shock and the bute would have killed her kidneys. She was anemic and had internal injury.
Sorry, don't mean to rant. (I do that a bit) i just get so irritated when I hear about people doing the "your over-reacting...she's fine" thing.
Good luck with your horse. It sounds like you rescued her from a bad situation. That was good of you to do. She is a lucky horse.