well an easy way to stop them from pecking too much is to clip the top part of their beaks with nail clippers-the part that overhangs the lower beak can be trimmed like a fingernail.
day olds with older birds is not a good combination, unless of course its their mom...but usually day olds are kept in a seperate cage or brooder until they can stick it out on their own with larger quail. crowding is also an issue. packed birds have bad tempers.
hope you get the problem sorted out!
-komori