It's very likely the light.
First, I do not buy into the whole 14-16 hours of light quoted as if brought down from Sinai on many threads. That's fine if you wish to push no account layers you're gonna process at the 2 year mark anyhow. Nothing wrong with that. But, if you want to split the difference between Au Natural, ie, doing nothing and the "light 'em up" approach, just add a couple hours of pre-dawn light. You'll likely be amazed. First year pullets don't often need much help, but if you add an hour or two of light, they'll lay very, very well.
Birds that are in moult, are going to take a break and I want them to take a break. After they've taken most of October thru December off, recharged, re-grown their new feathers then they too get the 2 hours of pre-dawn light, especially since I probably intend for these birds to begin laying eggs for February hatching.
Thanks. I only have three hens, lost 5 to coyotes earlier this year. Two molted early and completed regrowth about a month ago, one is just now regrowing her tail feathers. One of the early molters actually laid through her molt and was the last to quit as things slowed down, I was happy to see her take a break... Just not these younger freeloaders!