What's happening to these feathers?

[alaird]

Two of my Rhode Island reds have patches like this on their backs.. I noticed them shortly after the last of their baby feathers fell out, about a month ago. At first, I thought their adult feathers were just coming in slow, but these patches keep growing. Both roosters are about 3 months old. The other rooster has a bigger spot.
I haven't seen any parasites, fighting, or feather picking. My other 3 chickens are fine. Help!

 

[nuthatched]

What are you feeding them? A slow molt could be from not enough protein. If they were hens, I'd assume that they're over bred but they're rooster so I'm not sure?