corn is sort of like chicken candy. they love it but not really nutritional.
domestic chicken have been bred to produce huge amounts of eggs. wildfowl chicken may lay around 20 eggs per year, while laying domestic chicken produce up to 250 per year or even more. it's not something they can choose to devote energy to or not, so you can see why feeding them proper nutrition is important. sometimes i doubt even domestic chickens in a free-range environment rich with bugs, termites, lizards, grains etc would be enough to sustain them in health. certainly not on a limited range in subtropical zone, in winter.
the misunderstanding can be easy to make though. just a few generations ago chickens made 100 eggs max per year. the selective breeding is now very extreme for egg production, so chickens of those types aren't going to be healthy unless you are feeding layer feed of at least 16-17% protein (and a lot of people recommend higher than this). it depends on the chicken breeds you have too. we are pushing these birds to their natural limits, which can be seen in the shortening life spans and increase of reproductive disease, egg binding etc.
(also, so this post isn't all doom and gloom - there's actually upsides in that chicken nutrition is highly researched so they are actually getting more well-fed than their ancestors with proper vitamins (esp. winter) as well as increase in welfare in pastured and backyard setups, in contrast to farms in past where any trouble chook just gets made into soup 

)
tl;dr: yes feed them layer feed please lol