No, actually, you are much better off to edit, you can edit any time you want to, it is not an etiquette thing, it is the correct thing if your images are not sourced correctly. If you can, link directly to them and normally from now on I would recommend that you use Pixabay.com or Pexel.com or Unsplash.com, there are more royalty-free sites as well, but Pixabay is my go to, just for info.
Google, Bing, Pinterest, and those sites are image finding sites, they are not the owners or holders of the photos, the object is to see if we can find the actual artist to mention if possible.