I can't tell if the vocal sample is out of key or out of tone with the synths, but there's something odd going on there. I think it's because of how I expect them to lead the chord tones and they lead to a rather weak tone in the second and fourth chords. I like the chime-like synths a lot.
I think the Am vocal is in key, but it does seem to not want to resonate well with the 2nd and 4th which gives it that dullness you are describing. I could have spent more time chopping, but oh well. I appreciate your feedback tho, as always it’s great to gain feedback from more trained ears