You may end up losing this batch entirely but then you can start completely fresh and get the aquarium set up right for the next batch of shrimp!
If you do any large water changes then try and add the new water slowly, either dripper or some other way.
You should get yourself a TDS meter (as JayC above), they are cheap and readily available. You should always use a GH tester kit as well with shrimps, if you do the 50% water change that should halve the GH so you should get a reading after that, or if you can get a local fish store to test it for you that will give you an idea of the GH.
If your water supply is as hard as it appears it may be you will need to mull over how (or even IF) you want to keep shrimps as that may mean using RO or distilled/bottled water and buying a proper shrimp specific remineraliser? That will be quite expensive but you won't then have to mess about adding crushed coral/eggshells etc, but only you can decide whether you want to do/spend that much etc? If you live somewhere that gets a lot of rain, then you can use rain water?
Also, as JayC states, you need to know what you are using/adding to the water and aquarium, ie fertilizers, rocks. Unless you have very exotic plants you shouldn't need any fertilizers.
Just as a note, we have come across quite a few experienced fish keeprs that have this sort of start off issues with shrimp. Shrimp are more difficult than fish, and the aquarium and water etc need to be ready and within the required parameters before getting the shrimps. Usually people jump in, get the shrimps before everything is ready/sorted. Hopefully though you will keep at it, or if this lot die you will have another go and we can help you get it sorted?