Lost a Tiger Shrimp but rest of tank is fine?

Between 8:30 (lights out for my tank on timer) and 9:30ish, I ended up losing my heavily berried female tiger shrimp smh (just my luck huh?). She was curled up underneath my anubias nana, and had apparently just died. I turned on the tank light to look for any other surprise casualties, and found that the other three tiger shrimp were perfectly fine, as well as my 20 RCS and 6 b. brigittae-even my snails were fine. One thing of interest I did note, though: she had been grazing on my anubias mostly all evening. None of my other shrimp frequent that side of the tank, and if they do then they simply glide across the leaves and keep it moving. I had read somewhere about anubias possibly leeching toxic chemicals if cut and then grazed on-could this have done her in?

I've read that it could be a possible myth since my original posting. If that can be ruled out, then would pregnancy on top of the stress of a new environment (they've only been in the tank for a full day) be a better guess? I'm not sure how this effects shrimp, as I've never kept any berried shrimp aside from ghost shrimp.

Actually, I've begun to suspect something else. I've lost another tiger shrimp (male), and no doubt will lose the rest before the morning approaches. I'm assuming my water parameters must be off, but not bad enough to harm their other tankmates. I believe my water may be too hard for them to adapt to so quickly. I'm more than likely going to do a water change and see if that may help. That's about the only thing I can think of doing now. I recently had my water tested before adding them and everything checked out to be fine (at least for the other guys). Quite puzzled here =/

I've done a small water change and removed a rock that had been added today, scalded & scrubbed it in an attempt to clean it yet again to see if that was the issue. I'm going to leave it out overnight, and should I notice anymore deaths in the morning I can rule out the rock as the cause. So far the other two are swimming around doing shrimpy things So I have no reason to suspect anything out of the way I'd say. Guess I'll post in the morning and see what the night brings me :shakehead:

Update: Took the rock out last night, set it in tank water this morning and took that sample along with normal tank water to Petsmart to be tested. Turns out the rock significantly increased my pH from about 7.2 to around 7.8+. Going to do another water change to see if I can't reduce the pH a bit. Glad I caught this error before it took out more than just my shrimp (going on vacation for a week or two).