From your first picture of the cherries they dont look that healthy and that could have lead to your assasins attacking or feasting on them. And the Neons in there could have tried hunting them down since with that small of a school in that small of a tank. I personally would rehome the Neons, and if you do wanna do shrimp check around this site to see what people are offereing. Usually better deals and healthier shrimp than Fleabay.
Nice looking spec and desk by the way.