Welcome msfauss!

I cannot speak to the difference between the VIX and the NIX, and I also couldn't find much information about that type difference online. My DD had a similar difference when tested on the RIAS, and the the psychologist didn't seem too concerned about the disparity.

However the RIAS is considered fairly reliable and is often given in FL. If you feel there is more going on you may want to consider the WISC and it is not too early to test.