Im not an expert, but I do know chickens lay less in the cold weather. So given the timing, it could be either. Or both. You'd need to change feed to see if output changes to know if its a formula change or not. If production goes back up with a different brand, its the feed. Restart the TSC feed in the late spring and if the production goes back down its the feed. (confirmed)I have been reading this also on several sites , that feed from TSC could contain less nutrients than normal .
I suspect it is in more feed from just at TSC , because everyone that I know that has chickens has reported that their egg laying had almost stopped .....Mine included ( we have 23 layers ) and were only getting 2-3 day . Started supplementing our feed with fodder and we are now getting 6-8 day ( which is not bad for the winter )
And for the record ......I don`t shop at TSC . Rural King is my go to farm store .