The difference is quite noticeable by eye.
Then something is wrong. To answer your original question, it is not normal for there to be significant color changes within paper of the same type.
There have already been some good hints in this thread as to why this could be happening in your case. I'll just add that in our experience, 90% of the time a change is seen in a profile, it ends up being due to something changing in the profile creation process. Like Xilvar said, be consistent. Then again, it could be something obscure: Is one of the papers a lot older than the other? Red River Photo Matte will have some optical brighteners in it, and if the paper is old, it won't "fluoresce" like a newer paper does.http://www.colorwiki.com/wiki/Optical_Brighteners_in_Paper