Those are fairly heavy arrows, before you lighten them make sure you know what the manufacturer recommends, there is a minimum arrow weight for each bow.
A heavier tip will cause the arrow to drop faster.
Dropping 12" in 30 yards is fine if you know what you are looking at through your sights, seeing how your arrow is flying good at 20 yards 30 should be pretty decent too.

*edit* I am no crossbow guru, so take my info as that..
And welcome to the forums! Someone will be along soon to help..