I just noticed you edited your post to include a hypothetical.
Note that you (presumably the trustee) must follow the governing document (terms of the trust) when making (or not making) distributions. Further, state law controls in certain instances and federal (tax) law comes into play when you try to minimize income tax by using arbitrary procedures (i.e., that do not have substantial effect other than their tax effects).
Regardless, if the total ordinary dividends are reduced, then the qualified dividends should be reduced in the same proportion.
