#21 and 20 with the green symbol reminds me of a pharmacy symbol when I am traveling overseas. I look for that symbol on business in another country but it des not apply for me since you need to go to the hospital to get you IV infusion and meds. It just looks like a logo for an actual pharamacia. Not my favorites.
#19 and 16 are really cool and like how you used the hexagon with the O... BUT it puts the focus on the O....really trying to reinforce the "U" so maybe play with these based on the feedback you see from my favorites and rankings at this early stage?