large drop in eggs...

Our chickens are 10 mos old. They started laying in October. We got up to 7-9 eggs a day then during December and most of January dropped down to 4-5 eggs. The end of January we went back up to 7-8 a day. But this week we have only gotten 1 or 2 a day. This is the first bad weather we have had with snow (although we had some really cold weather in December). Do you think it is weather related? Or is something else going on?

 

I haven't checked them recently for mites or lice, but no change in feed. We were late getting them out this morning because the coop doors were iced shut - I felt so bad for them although they didn't come up much today either.