Chicken feed.
200' or 200 sq. ft.? 200 sq. ft. isn't free range. It's a pen and not sufficient to provide much forage.
Pasture, when green and succulent, will provide a good source of certain vitamins such as Vitamin A. Other than that, optimal nutrition requires all the other vitamins, minerals and trace elements.
According to the Manitoba department of agriculture
"It should be remembered that fresh grass is 75% moisture and while birds will eat lots of it, the grass will only account for up to 10% of their dry matter intake. Because the grass is less digestible than most ingredients used in poultry diets, it will supply only 5 to 10% of their nutritional needs. Birds on pasture should be fed a complete, balanced diet and the nutrients from the grass should be treated as a bonus. It would be foolish to believe putting your birds out on pasture will let you feed cheaper or poorer quality rations."
Table scraps, mealworms and a few greens won't come close to providing what they need.
I once had a guy want to buy hens from me. He said his birds had stopped laying after about 6 months. I asked him what he was feeding them. He said they foraged and he fed corn. I said what else are you feeding them and he said "just corn".
I said - "you're starving them."
Mealworms will be a good protein supplement but only a supplement.
You can find more info here.
http://www.poultryhub.org/nutrition/nutrient-requirements/
Essential things that
could be missing or insufficient of good nutrition unless one feeds a complete feed as the primary intake:
vitamin A, vitamin D3 and D6, vitamin K, vitamin E, vitamin B
12, riboflavin, biotin, pantothenic acid, linoleic acid, copper, boron, folic acid, selenium, manganese and phosphorus