Why get flagged for duplicate content?

You seem to have enough original content in your first recipe hub that HP considers it original, despite the fact that the recipe itself appears elsewhere. Believe me, if your entire hub was duplicated elsewhere, HP would have been on it like white on rice. I'm sure they have software like Copyscape that detects duplicate content quickly.

And the fact that you included a link back to the recipe in the second hub (called a "back link") will help the blog it appears on get more traffic, so you actually did the blogger a favor. You also did right by providing photo credits in your hubs, something you should always do when using someone else's photos. As far as I can see, you haven't done anything wrong.

Duplicate content is when your entire hub contains text that is an exact duplicate of text that appears somewhere else on the Internet, even if it is content you originally wrote (I'm not talking about plagiarism). Now with respect to "outside or back links," if you have a hub that HP has marked as Duplicate Content, it cannot contain any promotional links that go back to an affiliate marketing or similar site that you profit from. On the other hand, you can have as many outside/back links as you want in a hub that contains original content, but only two of them can link back to a site that sells something that YOU would profit from.

HP considers both types of hubs (i.e. Finally, if you publish too many (HP determines the amount; don't know what the magic number is) original-content hubs that only contain 1 or 2 promotional back links, HP also considers this as being overly promotional, even though you haven't gone beyond the promotional-back-link limit that HP has set in any one hub. I hope I haven't thoroughly confused you.

I wrote this hub when I first started writing here.