Last week I had 105 in the xsd tag and now I have 97? I'm sure I didn't get 8 downvotes in that time.
Can anyone help with this?
There are 2 options:
One or more answers were deleted (possibly together with the question they were posted on). You don't always lose reputation for that. Check the 'show removed posts' checkbox in your reputation history.
A question was retagged, so your answer no longer counts towards that tag. Sort your answers by recent activity and see if any of the posts that used to have the tag were edited.