I do not think the HOA is necessarily being outrageous. Its
job it to protect property values. When you bought your
place, did you not receive documents describing the terms of
ownership? Give the hearing process a chance to work. This
process exists precisely for people who might have
reasonable explanations/excuses and so should exculpated
from a fine.

It is outrageous to me that they are sending out a letter on Sep 26 on
an Aug 3 issue. The point of considering fines is to enforce rules on
non-complying owners. I have fixed the issue as soon as I could and
AFAIK have been maintaining the lawn in a reasonable condition for the
past two months.

To do this over an old issue is outrageous unless they are expressly
trying to be punitive rather than threaten fines expressly to get
people to get things done. There's no excuse I can think of for why
they are mailing me about this two months later.