Sure, why not?
Make sure to explain your action by leaving a nice edit message and/or comment, maybe something to the extent of
'Hey, I never heard of this disorder and had to google it, so I added one of the links I found to your answer for future viewers. If it contains any information that isn't correct or if you have a better/preferred source, feel free to change it.'
I see only 1 in which I would advise against doing so: If a question is on-hold, and the edit will not be to such an extent that it'll make the question eligible for reopening. Questions on-hold only get 1 edit that pushes them into the reopen queue, so I would wait until the necessary clarifications are made and then edit all at once.
Also, keep in mind that every edit will send a post to the front page of active posts again, so editing all old posts right now is overkill.