Do they leave food in the dish? If so, you're feeding them enough. Things that need to be considered are age, size of birds, if they're laying or not, and what you're feeding.
For example, a hen that has just come into lay, but is still growing, and is eating only scratch, will eat more than an old bantam hen that is past laying age and eating Layer.
It's hard to know with the info you've given. Something like this should really be decided at your own discretion. I would wait until they empty the bowls, then add some more, if they don't show interest, they're not hungry. If they wolf it down, you definitely need to increase what you're giving them.
Chickens won't overeat. If they're not hungry they just won't eat any more. If they need more food, they'll eat it. I think the only exception to this is when you have a treat like scratch or mealworms. I've NEVER had a chicken turn up a good treat.
chickens know when they are full, so no need to worry about leaving too much food. However, you would want to check for waste. Sometimes they would spill the feed just for fun. When I see excess feed on the floor, I would take away the feeder and the birds would clean up the floor.