My company, before I came on board, had created a few exact match domains for Product related keywords that they wanted to rank high in the SERPs for. They basically just copied (duplicated) content from our main domain onto the pages of these exact match domains.

Note: I have added canonical tags to the duplicate content.

My dilemma is as follows:

Nobody wants, or has the time, to create unique, useful content for these domains and I do not have the detailed product knowledge to do this.

So, my question is - are these EMDs hurting my main domain?

Also, what should I do with them:
1) Leave them as is without any newly added content?
2) Add 301 redirects back to the main domain
3) Delete the EMDs and all of their content?

Thanks-in-advance for any advice,

John