I picked up some Fluker's Reptile Vitamin with Beta Carotene. It says it has all the essential vitamins and calcium in it. Is this a good choice?

A strange thing happened though. When I dipped an earthworm in it, it started freaking out. A few seconds later, it started to seep a lot of blood through its skin. Is that normal?? Why would the powder hurt it like that?? I felt so bad for it!

My frog managed to eat one earthworm with assistance, but after that he turned his nose up at them.