I think you should feed crickets and other insect twice a day till adulthood or at least 6 months then you can drop back to once a day till a year old. After than a couple times a week should be alright. There doesn't seem to be a hard an fast rule about this though, noticed various sources seem to have different views on this. SOme books say 2 to 3 times a day for babies to 2 months old, then twice from 2 to adult. Others 2-3 times a day to 4 months old, twice till 6 months, then 2-3 times a week.
As one of your dragons is more heavier than the other...you could cut his back to once a day and keep the other on twice a day feedings of crickets. One question, do you feed them separately? The portly one could be eating some of the other's share of the food which would explain the difference in size (assuming both are the same age).