As far as I know, fair housing act does not prevent HOA to implement a rule like this. Fair housing act only prohibits a landlord discriminating against a tenant based on familial status. In the old days, again I do not have to research this, any law to prohibit the same family to live together is unconstitutional. Later, the Court changed its course such that as long as such law is reasonable, it would be upheld. As a result, many cities enacted laws to regulate the number of people residing in the same property. In your case those tenants are unrelated to each other such that the CCR is not in violation of pertaining laws. There are many unanswered questions, though. For example, is your property a condo, PUD, or SFH? How is the bylaw written regarding CCR amendment? How is a majority is determined? How is a quorum determined? When you bought the house, were you promised that you could rent to individual others? Are there other properties renting to multiple individuals? How do you know the CCR modification was just targeting you? If so it may not be reasonable. That is why I said you need to consult an attorney whether you have a case against the HOA.
Email communication is not per se invalid. If agreed upon beforehand by the homeowners this is a valid form of communication.
