Thank you so much, Takeshi. I really appreciate your input.
I doubt it has to do with link over-optimization. Our anchor text doesn't match the keywords in question which are 'web design' plus our location and our location 'web design'. They are very competitive words and I can see dropping several positions or to lower pages, but a sudden one time drop to out of top 50 seems to point to something severely wrong. Our competition at the top of the rankings have a lot of links and a lot more content than we do, so I understand why they are there, and it's possible that some newer companies have outranked us momentarily, but I am sure that the 50 or so ahead of us --- well, there aren't even that many web design or development companies here or nearby. Our domain authority, while it's dropped during this situation, is still higher than many. I think it may come down to a simple case of them having more links than us-some do and some don't, and I'll bet many aren't quality.
So true that there are no guarantees....and yet, I find it really compelling to try to figure out what happened. Not knowing what's broken makes it harder to fix and also harder to not repeat the same error- although, I have a lot of good ideas on what not to do in the future. I do get a little preoccupied by this question from time to time, but primarily, I've been working on creating high quality, relevant content and promoting the content in the hopes of getting links. As I mentioned, I'm on the cusp of trying to get some assistance with a link building campaign because I know it's a weak spot for me and I welcome suggestions of someone to work with.