Spotting of feathers apprearing on hed of hen????

I read through two threads on this subject and there was no real resolution of the situation. First I must say that I hope Im posting in the wrong topic area because I hope these spotting feathers on the heads of my hens dont amount to any serious disease or such.
Here are some pics showing both hen with and those without the spotted feathers. None had the spots but now some are beginning to show the spotting. Some are less than a year and others are all less than three years old. Some of my "oldest" girls are showing the whitening of the feather tips and others are not. The same goes for the younger girls.

Here is an older hen with the spots starting to show


Here is one of my younger girls (just starting to lay) with very pronounced white spots


Here is how they all used to look, without the spotting. Most of my hens are gray and only some are showing the white spotting on the head feathers.


I sure hope if anyone has any information on this subject that they will share it with me and others who have this same concern.
Thanks to all who offer any advice or just bump the thread in hope of catching the eye of someone "in the know"!

 

Really?? Were they getting the yogurt on their head feathers?
J/K no I havent been feeding them yogurt as mine birds dont seem to like it.
Thanks for the possible culprit though. I did pm one of the people in the threads I read and they told m that their hen was doing just fine, years after the post. They said that the feather spots never went away but at least the hen was still thriving. Im thinking it might just be a normal trait in some of the hens. It is so strange through. Id love to hear from others who have witnessed this in their flock.