Right to Amend Affirmative Defenses

I was served January 24th and responded well within the timeframe. Unfortunately, I just found you the other day, and the window to amend my affirmative defenses is closed. I am wondering if I can still file an affidavit. One of the bulletpoints in my answer was this:\"Defendant reserves the right to amend this Answer to include such other affirmative defenses as may be supported by evidence with a firsthand fact witness or law.\"Does this right only apply to that 21-day window given to amend the answer/affirmative defenses? I have attached my answer/affirmative defenses below. I didn\'t know what I was doing when I received the summons, so I had to act quick, and then I later amended the affirmative defenses within the timeframe when I learned more about them. Thank you so much!