At 12 weeks, they should be eating 4-6 dry ounces, each per day. You don't say how many you have. Give them a healthy early morning feeding. Check that feeder again in late afternoon. Is it still 1/2 full? Is it empty? As much as they'll eat, while almost emptying the feeder by roosting...
You don't state the age(s) of the birds. That information would be most helpful, as would knowing whether they have access to range and how rich the range is.