You don't know that for sure. Your body may only be able to handle a certain amount of whatever is in those pills at one time. For example, If you take several multivitatmins at once, you run a DANGEROUS RISK of taking in too much iron, which will lead to iron poisoning (and stomach pumping if you can make it to a hospital).
I don't know exactly what is in those pills, but if they do what they say they can do, it sounds like whatever is in those pills isn't something your body is used to processing. Take one pill at a time like the bottle says.