Hi Melissa, and welcome to the BYC communitiy
From what I gather so far, there might be several things going on.
A feed with lots of corn is not appropriate for laying hens and usually lacks in protein and other essential nutrients which can cause a multitide of issues.
As it is cold where you live: Do your chickens have fresh liquid water avialable at all times? Do you use a water heater? How often do you clean the waterer and what do you use to disinfect it?
Do your chickens have crushed oyster shells (calcium) and grit (crushed granite) available at all times?
What age are your chickens and how old is the male? Were they all raised together or did you recently add some chickens to your flock?
Just like the others already mentioned, it is important to check the feed for mould and parasites, as both can have detrimental effects and even lead to death. Pelleted feed should not be older than 5 month, so check for the mill date on the bag. And depending on how it was stored, might even be off way before, so always look closely and sniff carefully to check the freshness and quality.
Laying hens would need a feed containing 18-20% protein with a calcium source( oyster shells) and grit in a separate dish always avilable.
Whend did you last deworm them?