Its not that iceberg lettuce is bad it is just that its basically water and contains hardly any nutrients. Romain, buttercrunch and redleaf are better choices - they contain some nutrients and are more palatable to chickens.
My hens love tomatoes, zuchinni, yellow squash, *pumpkin, *butternut squash, lettuce, sweet corn, water melon, *cateloupe. honey dew, green beans, *kale, apples, strawberries, *carrot peelings.
*good for orange yolk color