Contact your beneficiaries and your trustee. Under the laws of your state, you may be able to amend a trust with the consent of the trustee and all beneficiaries of the trust. This would require written agreements from everyone involved. In some states, such as California, modification under these circumstances does not require court approval.
Draw up a second trust, if this course of action is better suited to your desired outcome than simply amending the old trust with the consent of all parties. This is known as a "decanting" trust, in which your trustee distributes assets from the old trust into the new one that contains revised goals and instructions. The second trust may contain a new arrangement of beneficiaries that will be subject to state law. There will also be tax consequences for any assets sold or transferred into the new trust.
Sell interest in a business or property out of the first trust to a new trust, which then benefits from all the gain in value of the business or property. Your trustee must have discretionary power to carry out this step. The first trust retains its irrevocable terms, but the second trust becomes the vehicle for distributing the business share and the growth in its value among its named beneficiaries.
Petition the court to allow an amendment to the original trust, if you can show that a "scrivener's error" occurred when the trust was originally set down, or that you did not understand the terms of the trust when you signed it. You do not need direct consent of the beneficiaries to take this step, but the beneficiaries do have the right to raise an objection to the amendment. If the beneficiaries do not agree to the amendment, the modification must be reviewed and approved by the court.