I was just looking over the ingredients for these caps, and they kind of remind me of the GNC Mega series. One of the issues I have with these invovles the fat soluble vitamins (A, D, E, and K). They really praise the enormous mounts in these caps, but fat sol vitamins are actually toxic in large quatities. If you already maintain a nutrient dense diet, you may be experiencing negative effects from that.
Personally, I never take my vits and mins together, because some counteract the absorption of others.
Also, if you can find Perfect Iron (Iron Oxylate) it is easier on your body...nausea is common with the iron in these caps.
...could just be crap ingredients too, like sofa said.