Is my hen molting? Any molting info would be helpful :-)

My lovely Mildred seems to be losing her feathers!
She's not really been acting herself recently, it doesn't seem like she's ill, just a little less active and a little less interested in her food.
She started losing a couple of feathers a few days ago, and now there are feathers all over the nest box when I go to sort their bedding, and when she preens herself feathers fall out. My other hen Gertie has taken to helping her preen herself to get rid of the loose feathers!
I know that chickens do molt, so I'd just like to know why they do this, if this is what she is actually doing and what I can do to keep her at her happiest while she grows her lovely caramel coloured feathers back.
My hens are rhode island red hybrids and they are both about a year old.

My 3 have been having a wee moult and not had an egg for 2 weeks now but they seem to be getting over it.  Protein is good with helping new feather growth.  Try giving them a treat of Tuna in Spring Water.