Cast On Gems not working

So I tried putting two Cast on Freeze for more comets rain but something weird occured : I have two sets, 1 is for Ice and 2 is for Lightning. I have 135 spirit in both which is enough to activate the two of them but beside having better stats in the Ice set nothing change much, except : My second Cast on Freeze only activate with the Lightning set. Someone on the forum already saw this issue with Cast on Ignite and that's why I put "Cast on Gems".

But no one told him how to make it work. I mean, it can work because both activate on my lightning set (beside it being useless) but I just don't understand why the gem don't activate with my Ice set beside it being only better in every way...