Unintentionally disrespectful in the Statement of Purpose/Academic essay

The culture regarding the academic titles is quite country-specific. In some countries (e.g. Germany) academics are more often referred to by title and surname, Prof. Famous, even in a classroom. In some countries (e.g. UK) students will address their lecturers by their first name, but refer to them by their title and surname in official writing.

However, these traditions rapidly change now because of the cultural mix in academia. With the growing numbers of professors with unusual names for European cultures, it is a more common practice now to include both name and surname after the title, e.g. Dr. Hu Rich. It is impossible to maintain the same standard, and I don't think that academics generally care too much. It is still considered a good tone to keep the titles in official academic writing, but I don't think we expect all MSc candidates to know this.

Overall, my advice is: don't worry to much, don't write to correct it, just make sure you do it properly next time.

There is, of course, no guarantee something won't hurt your application. There are some people who care deeply about being addressed by their title, some for good reasons, some out of culture, and some just because.

But honestly, I very much doubt most of the people reading your application will care. An SOP is not a driver of admissions in most programs, often being used instead as a way to gauge whether or not you have any idea what you're actually signing up for, etc. A minor error like that likely won't matter. I would relax and let it go. Emailing the professors in question just draws attention to it, for little gain.

I failed to address those Professors with a respectful title (I mentioned A and B, instead of Profs A and B).

You are confusing addressing with mentioning (or referring to). When you refer to a researcher, the name is sufficient. If I understood you correctly, that is what you did. That’s fine.

It’s when you address a researcher or professor that using a polite title is appropriate, such as “Dear Professor [Surname]” or “ "Sehr geehrte Frau Professor Doktor [Nachname]."