When you say the businesses are in no way connected you need to be able to prove that I think. If you are optimizing for all of them I assume you are using similar backlink techniques etc so you link profile and site names all look very similar which may have flagged this up to Bing. Generally being an SEO for 3 different businesses all competing in the same market may reflect a conflict of interest anyway...

I think that is surprising for me too. In my opinion may be there are some spamming problems.If you can show the link of Bing mail which you have been received from them, then i can say something about that.

if u do more spamming then it will blocked your website.
contact as soon as possible.