Recently, I've been dealing with sudden shrimp deaths, where the shrimp will end up slowly becoming sluggish and not avoiding my tweezers when I try to replant plants. I try my best not to kick up a lot of debris. Most of the time, shrimp turn pale, before dying like in the picture.
I've had a mixed grade of Cherry Reds in this tank and they've been doing fine up to the point where I went home for Spring Break two weeks ago. A week ago, when I came back from Spring Break, I found several shrimp dead or dying. I had done a 50% water change before leaving for break and I believed that the shrimp should've done fine like they usually do.
This tank is an EI dosed, co2 injected tank, and while this may usually have mixed reviews between people when it comes to taking care of shrimp, I've read that shrimp can normally handle this.
I do water changes straight out of the tap and here's the parameters:
Tap:
pH: 7.2
Ammonia: 0 ppm
Nitrite: 0ppm
Nitrate: 4ppm
TDS: 295
I haven't checked KH or GH recently but after tests I have in class today, I'll try to test them to see if this adds to any problems.
I'm thinking of getting distilled water mixed with Tap for this tank so that I can lower the GH and TDS somewhat.
If you guys can find something wrong with my shrimp, please help

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