Hitech filters... colour cast?

I've recently upgraded from cokin P filters to LEE 100mm because of the colour cast I was getting when stacking cokin filters.

I have a set of Lee hard ND grads but am struggling to find a soft set at a decent price but while looking found some 100mm hitech ND grads (set of 3 ND grads with 3 full NDs for £125!).

Question is how neutral are hitechs? Ive read theyre pretty good but what about when using more than one?

Are they as good as Lee or am I better off spending the extra and getting lee as I know theyre good?

I use Hitechs and notice a slight magenta cast when stacking in certain lighting conditions. But it doesn't bother me much. I'd get the Lee's if you have the extra cash just for the peace of mind if I were you.

I used the hitech in the cokin p size. now that ive upgraded to the 100mm size I only use lee or singh ray. There was a definite color cast when you stacked the hitech with any other nd filter.