If they're getting a fortified laying mash, pellet or crumble they won't require additional vitamin and mineral supplementation. If they're eating a fortified general purpose feed they may require supplemental calcium, but nothing else. If they're not getting a fortified feed what they need in addition to or in replacement of what you're feeding is dependent on what, exactly, it is that you are feeding.
Here, the feed mills add the vitamins and minerals to the grains when they mix feed. Is it possible that your feed mill is adding anything like that to the feed?
Do you know what grains they are putting in the feed? Anything for protein? Like legumes or fish meal?
Are the chickens locked in a pen all day or are they loose? If they are loose during the day, to eat grass, leaves, bugs and worms, they may be getting lots of different vitamins and minerals on their own.
You have to be careful adding fat soluble vitamins and minerals to your chickens' diet, because if you give them too much, it can be bad for them. That's why we are trying to find out what they are eating and what might be in it.