Help with multivitamin?

Hello, I've got a question about this multivitamin my family and I started taking today. It's the GNC AMP Endurance Vitapak Program, the guy working at GNC recommended it, and it was buy one get one half off, so I thought, "Wow, great deal!". I've taken multivitamins before, but this one had my whole family and I feeling crazy jitters, we literally outstretched our arms and kept our hands flat and just watched them shake uncontrollably. It was such a weird feeling, and then my brother became violently sick, no one else got sick like he did, but he can't relax because of the jittery feeling. I've read that a lot of the nausea from multivitamins is because the iron is too harsh on the stomach, but reading the supplement facts on all the pills, I can't find any iron in these, and it says nothing about caffeine either. Anyone know what's going on?