Check the scribed mold number on the blade near the hub (1,2,3,4,) if they don't match, neither will the weight of Your blades.

Try to get them out of the same bag, if not, You definately need to balance them. You won't believe how much one can weigh next to another one of a different mold. I've had it where My heli was almost unflyable just grabbing two out of a box of mixed.

Gary