It used to be an issue that portfolios had to have the right balance of capital growth and dividend income to maintain impartiality between income beneficiaries and remainder beneficiaries. However now, you can just make an adjustment and distribute the growth as income. (Or alternatively, use a unitrust.)
Typically, trustees who are also beneficiaries do not have the power to adjust. However, they may be able to convert the trust into a unitrust with judicial review.