Whats wrong with hens?

i have two hens both are rhode island red/ white leg horn mix. both are roughly 2 years old. one of my hens has stopped laying eggs completely and they other one is laying white eggs instead of the brown eggs she usually does. they both have a large fenced in area with the option to go inside, are fed corn, lettuce, chicken feed, eggshell and grit and always have fresh water, so i am not sure what is going on. are they just getting old?