Really just a cosmetic thing, I think
[monitors](19) should be merged into
[monitor](290). It makes sense not to fragment the tags based on a plural. I guess, as well, this should be added to the list of tag synonyms (when it's implemented).
Actually, Super User has a multiple monitors tag: [multiple-monitors] (435 questions). This is the tag to use for discussing setups where multiple monitors are being used simultaneously. We use the [monitoring] tag for questions about monitoring software, but they can be easily confused so it's good to watch out for that.
Several of the existing [monitors] questions already have the [multiple-monitors] tag as well, and a couple of the others should have the multiple instead of the singular. I've fixed those manually, and batch-retagged the [monitors] tag into [monitor].