Kaggen

I'm a bit confused, seeing as how the first 2 screenshots go against the theory, being that the first depicts both spells as being non resistant, and the 2nd showing both being resistant, yet you didn't resist the following blizzard V. More than likely though, it probably just has relatively high magic evasion, which causes spell damage to widely fluctuate regardless of innate resistances to certain elements.

Honest to god though, I'm not going to spend a lot of thought on this, it is a Nabis thread after all, which following posters need bear in mind.