Lost all my shrimp over 4 days.. urgent

[malekn]

Hello. I bought 12 shrimp snd put them in a small 5 gal tank with amazonia and some plants. The rocks and substrate were cycled for 2 months prior to that.  I added the shrimp about 2 weeks ago. 2 of them died in the first week randomly and i gave it no attention as this happens with new livestock. Everything was going well and they were eating until 3 days ago, found 2 dead shrimp next to a molt (pic 1), later on in the same day found another one dead. The next day 2-3 more died. And whatever was left died over the next 2 days. On the second day, i thought i saw planaria so i got some medicine and started treatment but it did not stop or slow the deaths. Im really flustered here please help. Unfortunately i do not have test kits but i know my water is 400 tds. 

[malekn]

Note: just checked my tanks water, it read 850 tds. Im not sure if this value is true or just elevated because of the medicine. Assuming it is true, would it be the cause?

[Vince1080]

it seems like something is wrong with the water quality you really need to at the least check the PH... you can get ph testers in pen form for cheap on eBay... Note I am in no way an expert but I have kept shrimp for a while.

[OblongShrimp]

Amazonia is a buffering substrate that is meant to be used with soft water (usually RO). Based on your tds you are using tap water with it which will eventually overwhelm the buffering ability of the substrate. That could be stressing the shrimp. Where did you get the shrimp from?  Pet store or people selling adults often import them and they are not always particularly healthy.