Lovely little playground you got going on there for them BV's.
One thing I'd suggest you not do anymore is to stir up the substrate with a gravel vac. This only creates spikes in params which eventually kill shrimp. What you can do is gently wave the vac across the subtrate surface without actually touching it and suck up as much mulm as you can. Otherwise, just toss in lots of moss and floaters in there to suck up the nutrients and leave the mulm alone lol. I also think those mystery snails need to go (no offense because I know you love them dearly) but they excrete wayy too much poo for my liking. And they eat plants! haha
Sorry to hear about the deaths... stop messing with your substrate!
*edit* you already took out the mysteries! Great... what are batikis? lol Do they poo just as much?