Time to attack the Ice Court?

Hello Total Warhammerers, I am playing through the Realm of Chaos campaign for the first time, I am around turn 130.

I have been ignoring the Chaos Rifts for the most part, after an early game attempt went badly. So I have been working to close them and build protection buildings to keep them from spawning. I suspect this may be a bad strategy for the campaign victory conditions, but that's a problem for another day.

I am currently at Strength Rank 6, with 2 full stacks of RoRs and another stack of 15 mixed units. I can max out that army but my income won't support much else at this point.

I have defensive alliances with most of the remaining Chaos factions at this point; most of them are significantly weaker than me, except the Seducers of Slannesh who are close to my rank.

The Ice Court is rank 1, and they are allied with Wissenland & Nuln, who are rank 2. I share borders with both of those, and most of my allies are already at war with them. I am not at war with anyone currently, and a wave of chaos rifts just closed.

Is it time to declare war on the Ice Court? Doing so feels like suicide, but I don't really see anything else to do at this point. What would you do?