Hi
I'm afraid that is not moulting after all. It's either feather picking or lice I would guess. Have you examined them thoroughly and familiarised yourself with what to look for as regards lice and mites too for that matter although I would expect them to be seriously anaemic by now if mites were the problem. Have you spent some time observing them to see if they are excessively preening, particularly at night on the roost or some of them feather picking others. Did you fix them up with a dust bath? Personally I use DE and have had some success with it. There are conflicting views on it's use though as you have already read. Here in the UK there is a brand name DE called "Smite" specifically sold to target lice and mites in poultry, which I have used a couple of times with success and once when it failed to get on top of a serious infestation of mites, but then it took numerous applications of various products including permethrin to bottom it. I've not had any problems with birds having bald patches like that outside moult though and even then, moult tends to be more neck and back and should be sorted in a couple of months or at least see significant improvement. Yours have got noticeably worse since your post at Christmas.
I'm also concerned that those hens look quite bloated. Those bald abdomens look much rounder than I would expect in a healthy hen, although it may just be the camera angle or a trick of the light. What are you feeding them? I'm thinking diet may well be an issue here with both feather loss and abdominal swelling.
