(a) By right. HUD may amend the charge or notice of proposed adverse action once as a matter of right prior to the filing of the answer.

(b) By leave. Upon such conditions as are necessary to avoid prejudicing the public interest and the rights of the parties, the ALJ may allow amendments to pleadings upon a motion of a party.

(c) Conformance to the evidence. When issues not raised by the pleadings are reasonably within the scope of the original charge or notice of proposed adverse action and have been tried by the express or implied consent of the parties, the issues shall be treated in all respects as if they had been raised in the pleadings, and amendments may be made as necessary to make the pleading conform to evidence.

(d) Supplemental pleadings. The ALJ may, upon reasonable notice, permit supplemental pleadings concerning transactions, occurrences or events that have happened or been discovered since the date of the pleadings and which are relevant to any of the issues involved.