Yes, adding information is fine (if it’s not too much at once).
Quoting from the Help Centre on editing:
When should I edit posts?
Any time you feel you can make the post better, and are inclined to do so. Editing is encouraged!
Some common reasons to edit are:
- to fix grammatical or spelling mistakes
- to clarify the meaning of a post without changing it
- to correct minor mistakes or add addendums / updates as the post ages
- to add related resources or hyperlinks
I think that adding a small amount of new information (such as in this example) falls squarely under the third item, and so is perfectly acceptable.
You have to be more careful with edits that add substantial content. In particular, be careful of running into this rejection reason:
This edit deviates from the original intent of the post. Even edits that must make drastic changes should strive to preserve the goals of the post's owner.
It’s harder to come up with a rule-of-thumb for this; I don’t think I’ve invoked this rejection reason very often (on SFF, at least).