They are probably okay to be on their own.

If you're worried, what I do when I wean a little younger, is I take the rodent block, and put it in a shallow bowl of water, so it's soft. They get hydrated and the food is easier for them to chew.

Also, looks like you have a blazed rat (the one with the "V" on it's head)
Be wary about breeding that one since blazed have a tendency to carry Mega Colon, and high whites from blazed lines are notorious for that! ;-)