I wouldn't say "ripped right out of QFGV," but no, it's not just you. There are some textural similarities. I didn't write out the chord progressions (underlying movements in the harmony, usually best heard in the lower instruments) to see if a key moment in which those corresponded might be heightening the sense of familiarity for you, but often that's what happens for me when I hear similarities in things that otherwise don't share melodies.* Certainly the string line in the Apothecary theme and the acoustic guitar line in the Erana's Garden theme are both much more "active" and ornate melody lines (embellished with more notes) than James Newton Howard's music for "Blood Diamond."
At any rate, the similarities are slight enough that I'm pretty sure they're purely coincidental. I don't imagine Chance Thomas' score for QFGV is very high profile among Hollywood film composers, and we could probably find numerous other pieces that would serve just as well for influences on James Newton Howard's music in that track. The musical palette is really quite limited when you think about it, especially if we're only talking about tonal music in the western world. It's amazing that composers squeeze out as much variety as they do!
* Actually, it would be a fascinating psychological study to investigate what elements most frequently cause people to hear similarities between one piece of music and another. For example (let's use melodies, since chords are harder to discuss), when one melody calls another to mind for me, it usually isn't because of what you'd think, that the melodies share a large percentage of notes (i.e. 80% is literally the same, with only 20% different). Nor is it even necessarily that both melodies share the same skeleton (meaning that if you take away the embellishing notes and left only structurally necessary notes behind, they would both move in the same fundamental way, i.e. from tonic to dominant and back again-- DO RE MI FA SO FA MI RE DO), though I do sometimes hear this source of similarity in melodies as well. Instead, it often is just because the same large interval (like a major sixth, i.e. SO up to MI) is used in both melodies in a key location. In other words, just two notes from the melody can form the impression of sameness for me. Weird, huh? I may be an atypical case, however.
I hope I am explaining enough that even with several music theory terms in there, what I am trying to say can still be deciphered. If anyone reading this wants me to re-explain something, I will gladly try.