I'm using a Kaiser with multigrade head and a Kienzle T67/69 with digital color head.

I'm aware of the problem, that i can't expect to obtain a real grade 5 with a color head (or even 4, at least not with every paper). But as mentioned, even with white light (no filtration) i only get about grade 0.5, and just about grade 2 with full magenta, which definitely should not be the case with fresh paper.