moulting..how often and when?

[spish]

im trying to figure out whats causing the feather loss in some of my hens..and someone said they could be moulting (seeing as theyve been treated for lice/mites) but i thought they only moulted in the autumn (its now the beginning of summer here?)
its only feathers missing on their necks at the moment (at the side) but its the roo and three hens (otherwise i would of blamed the roo..but seeing as he has it too....) and its only the older birds...(2 years and above) none of the birds from this year seem affected......?

(sorry if this is in the wrong section..it didnt seem like an emergency so didnt want to put it there!)

 

[Cindy in PA]

Chickens should molt after a year or more of laying. So if they start at 5 months and are good layers, they will molt at 17 months or older and then every year after they lay for 12+ months again. I have never had chickens molt in a certain season. April hatched would molt in Sept-Nov and July hatched in Dec-Feb.