No problem over their not liking corn, as it really isn't necessary for them, and too much will encourage them to put on unwanted fat. If you want to try something they are sure to love, to help get them to come to you and become more tame, try a sprinkle of hulled sunflower seeds. Get them from a bird food supplier, not a health food shop, as they'll be a lot cheaper. Sunflower seeds are very high in protein and unsaturated fats, so they're good for the birds, and a suitable supplement. I'd go easy on the sweetcorn, which is maize, and the potato, so also fattening. Just stick to growers pellets most of the time, especially as they're lucky enough to free range your garden.
I do wonder why they don't like the corn, though- they're certainly not too young to eat it, and I thought all hens went mad for what is, after all, their natural food. Has it got a lot of chopped maize in it? Or is it mainly wheat? Wheat is better for them than maize, and so long as it's fresh and not tainted in any way, I can't think why they'd not want it. Has the bag been open a long time, or was there an expiry date on it when you bought it?