Young bearded dragons should be offered as many crickets as they can eat in a 5-10 minute sitting 2-3 times daily. Fresh greens should be left in the cage at all times (changed once or twice a day depending on how fast they wilt under the lamps, good to keep them away from the basking light anyway).
Dust one feeding of insects a day with calcium and vitamin powder.
Also, since it sounds like you have them all in one cage, would be a good ideal to prepare individual housing for each dragon, this makes it much easier to monitor individual growth, how much they eat and poop. Also, it avoids stress by dominating dragons trying to get all the food, best basking spot etc. Also, by 6-8 months of age, males start to get sexually mature and if more than one male in the cage, there can be fighting, sometimes very severe fighting between them. If all females, you may be alright but even females may not get along and can fight. Another danger is h aving a male and female in the cage as the male will attempt to breed the female, whether or not she is physically ready or not. Females should not be bred at all till they are at least 15 months old, if not older. Many breeders recommend 18 months or older before breeding. Also, if the dragons are all from the same clutch you don't want brother and sisters breeding.
So, males and females will need to be separated at or before they reach 6 months old. Breeding behaviour may not be evident at t his time but once breeding behaviour begins (male showing black beard, head bobbing, trying to mount the female etc) usually it's too late to stop mating from occuring as most likely it has already when you were not looking.
Remember, in the wild, young bearded dragons have an option they do not in a cage. They can run away from males for many yards if needed. In a cage averging 4' long, not alot of room to run away.
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PHLdyPayne