Heres an observation I made after looking at the close ups of your pieds. Did all these birds come from the same place and if so, do you know if they had any greens/spauldings on hand? The reason I ask is that in a couple of your pics they look to have a little green in them due to the "tear" shape in the crest and their cheeks by the ears look to be yellow. Healthy greens will start to show the yellow at around that age and it usually starts at the ear vent and grows forward with age. Im probably wrong, hard to tell from pics but time will tell please keep us posted.
Gerald Barker