A slow gradual feather loss is pretty normal, as long as the pullets are not becoming bald. New feathers will grow in to replace the ones that fall out.
Usually pullets will go through one or two "mini" molts before they start "true" molting. I've heard at 6 months and 12 months.
True molting is in the fall (since most chicks are hatched in the spring) it is often at about 18 months.
Now that being said... I've had chickens about 12 years now, and have had only 1 chicken truly molt in the fall. And never had a pullet "mini" molt. Just a year round gradual feather loss; with an occasional bald spot.
I've speculated that the mild climate here is the reason, but others have reported the same thing in more extreme climates.
lighting can sometimes effect molting as well.
Russ
Hi Russ.... Thanks for writing this. It was something I'd heard but forgotten the timing on. With two new chicks I wanted to have an idea of what to expect.
I read something else that might be interesting to include here. Sorry I can't remember the source (swiss cheese memory). The article I read said that those hens that go thru a really heavy, fast, molt (and look like they went thru a plucker) are generally the most productive layers. They get in there, get it done, and get on with life. As compared with the ones that shed a few feathers at a time over an extended period... just piddle around at it. I don't have the experience to agree or disagree but thought it was interesting.