The third is definately a man. From the frame I'd say it's either Keith or Colby. Definately a big guy. Wouldn't think it's Nick or Jeff from the size. If you have a good picture of Keith's rain gear, it might tell the tale.
Fourth person appears to be female.
It is not clear to me that there are 5 people in the pic. There MAY be a set of legs showing on the bridge. Again, I'm not convinced there are 5 though. Although they probably read it everyday with their morning coffee.