I'd weigh each round. You should find that they average a fairly constant amount (+ or - a grain or two), but there will be some that are significantly below that average. Pull any that you have any doubts about. Personally, I'd shoot the remainder being very careful not to fire into a squib.
You might even purposely load an empty cartridge (case, primer, no powder and with the bullet barely in the case for easy removal later) and see what it weighs. That would give you a good benchmark for what an empty should weigh.