Their voices are entirely right. I normally don't read cutting fics for several reasons, but you've got me sticking with the story anyway.
Since you asked for concrit as well, I would suggest making Sherlock more precise in his word choice (a specific toxin instead of botulism and maybe "for a moment" instead if a second) but I am being ultra-picky because you were brave enough to request feedback and I get frustrated when I'm trying to improve and people don't say anything, or worse yet, say they don't like it but don't say why)
Looking forward to more of this!