Often the board is limited in what it can do and how it must be done. Many HOAs enact "policies" that do not conform to the CCRs (declaration of covenants, conditions and restrictions). Policies may fit into the CCRs or may not. The adverse action procedure is also often described: what notice must be sent, what must be in the notice, how long the owner has to respond, and so on.
My personal experience is boards never read the CCRs and don't understand what they did read. They usually rely on professional management companies to guide them, but they don't read them either. They go by what they have done in the past. And they have lawyers on staff to guide them.
The unfortunate reality is that as a homeowner you cannot appeal to the Justice of the Peace Court, which handles small claims and the like.
Appeals of decisions made by the board to levy fines may not follow their own "rules" and certainly ignore the CCRs. Worse, you can't appeal those appeals to the board by going to JP court. It is simply too expensive to challenge.
You have to go to County Court, which requires an attorney to sue for you. So, inequities in the way the board acts, sometimes not following the CCRs or abusing the articles, go unquestioned and unchallenged.
Ask your state representative to change the law to make JP Courts a first line of judgment about bad HOA actions. At least then you can afford to challenge bad conduct.
In this particular case, only an attorney can give you advice on whether the board can change the rules.
You might look that up in a legal dictionary or ask your family lawyer.
We're typically not lawyers here and these are probably points for a lawyer, but my guess is in the past they have not imposed fines as a courtesy. They did not grant themselves the power, they had it all along, but did not use it. I'll guess the homeowners did not have to vote on this provision.