Esther 2:3 ends with the word תמרקיהן. Esther 2:9 contains the word תמרוקיה.
The question is about the sh'va under the mem. My source, via Kinnor software, says that this sh'va is na in the first case but nach in the second case.
Since the vowel under the taf is patach in both cases, I would have said that the sh'va was nach in both cases; otherwise the word starts with an open unaccented syllable with a small vowel. But nobody should listen to me since I don't know the first thing about it.
A difference in the words is that the first is mil'ra, with secondary accent (though unmarked) on the second syllable, while the second is mil'el with secondary accent (also unmarked) on the first syllable. Presumably this difference of accent has something to do with it, though the rules I know for sh'va na still say both would be nach.
Can someone please explain what's going on?