Sounds to me like you may have sighted in with 100 Gr. Field tips and your Broadheads are 125 GR. If so that's the problem right there. when sighting in with 100 gr field points then you should use 100 Gr. broadheads just keep the weights the same.... IF that isn't the situation then you need to Re-Sight your bow. make sure your nocking point hasn't shifted up or down and make sure your rest is nice and tight on the riser......
Good Luck and post pics when you get that big 8 pointer