Davekrista,
I have run out of ideas - -
1.) You are not too hot - - #1 reason for production loss right now.
2.) You don't have too many roosters stressing out the girls
3.) You don't have a external parasite issue - - no missing feathers
4.) You aren't having flock conflicts - - - no missing feathers and flock has been together for 4 months.
5.) You haven't experienced any changes - - other than food
6.) You don't think worms are the issue
7.) No signs of predators . . .
8.) Nobody is molting - - no missing feathers
NOTHING IS LEFT - - - except the food.
I am really surprise that going from one form of laying feed to another form of laying feed
would cause such a total shut down on egg production.
At this point, I am with others on this - - - switch back and see if the that fixes the problem.
Good Luck