I think that it is appropriate to credit the autor as you are using the assets in and editorial style. There is, however, no imposed place to place the credit. I generally place credits near the picture, so that I do not have to think about updating, when I change an asset. I just change to the new credit line. However, if you are using less pictures or you have a specific place where you put the credits, you are free to put the credits there.
Look here for more information on licensing: https://community.adobe.com/t5/stock/links-for-licensing-terms/td-p/11366788 (Disclaimer: As always with licensing, this is my interpretation of the rules. I think they are correct and advice is based reading and interpreting the license terms and on fair use for both the buyer and the artist/stock company, but I can not rule out that my interpretation is wrong. I'm not an Adobe employee)
ABAMBO | Hard- and Software Engineer | Photographer