New owner just 6 months..first issue with a hen...need advice

I am new as well but it could be the start of moulting maybe. Just an idea as I am new to this since April so I am not positive. Hope someone else chimes in......Good luck!

 

if it's mites or chicken lice look around their vent after dark with a flashlight..... report etc....

 

If you see dotted specs it sounds like mites. Here is a helpful website:
http://ohioline.osu.edu/vme-fact/0018.html

Here is how I apply powder to my birds:
I line a cardboard box with a large plastic bag to catch the excess powder.
I put a chicken in, so they are lying on their backs and hold them by the feet.
Then I take a tied-off sock or stocking with the powder in it and powder-puff them under the wings, by the vent and everywhere except the face.
Take shower afterward, wear long sleeves, wear mask, etc.!

Repeat in 10 days otherwise it'll happen all over again.