My chickens have too experienced light moults- I just see feathers on the coop floor but nothing substantial missing on the hen and then I have had chickens have complete blow outs and it took six months for one of them to feather out again. I had one RIR production bird, go completely bald on her back, I thought the rooster may be being too rough but there were no sores on her back from his claws, I thought she had mites, but no. And then when she did feather out (6 mos.), she started to develop rooster characteristics- she has a large rooster like comb and long waddles and little spurs. She still lays but the eggs are either shell-less or have paper thin shells. I credit the genentic messing arounds at the hatchery. But anyway.......
How old are your hens? I have hens have a light moult in their first year but by the second- poof- they look like they got caught in a feather puller.