No need to file a supplementary affidavit. Your case being a civil matter, you may file an amendment application u/Order 6 Rule 17 CPC. Concisely state the reasons for amendment (in your case, it would be the grounds). After stating all facts brusquely, mention that: (i) your amendment application is filed on bona fide grounds & would not adversely affect your opponent party; (ii) it does not introduct any new fact & is purely technical by nature (iii) that it(amendment application) is necessary to determine the real issue-in-controversy between the parties & (iv) if disallowed, it is more than likely to cause you severe irreperable loss& hardships which cannot adequately be compensated monetarily.
In your prayer, request that: (i) the court allow your application & permit you to amend the same & (ii) pass other orders in the interests of justice.
After following the prayer step, file an affidavit mentioning that: (i) you are the party (plaintiff/defendant) in your suit & are conversant with all facts/circumstances; hence competent to swear the affidavit; (ii) all statements made by you are true & accurate and nothing has been concealed therewith; (iii) contents of your application & annexures are true copies of the original. Put a verification statement and swear it before a notary public, prior to submitting the same before the court where you intend to file your amendment application.
If you have any queries, you may contact at: firstname.lastname@example.org. I shall be most happy to advise you on your case.