Why are my shrimp dying

[Mapshrimp00]

Hi guys, for the past 4 weeks I’ve been losing shrimp at a rate of about 1-2 per day. Some days none are dead some days some are. It’s been constant- I wake up in the morning turn my tank light on and see the little guys who have met their peril. 
 

i have red cherries and Some armano shrimp in the aquarium. Only 1 of the armanos have died during this time and showed the same behaviour as the cherry shrimp when it died (I will attach a video to show what it looks like). 
 

i have tried dosing H202 at the correct dosage for 5 days before doing 2 40% water changes the days after. 
 

i have dosed esha 2000 in the tank for the recommended 3 day course followed by a 40% water change which had no affect - although the deaths did seem to slow down. 
 

i do a small 15-20% water change each week.

 

The tank has been established for about 7 months and the cherries I’ve had have successfully bred during this time. I started with about 12 baby cherry shrimp and the colony exploded to well over 100 shrimp. Since then I’ve lost about 40-50 shrimp in this mass shrimp death. 
 

i did buy 10 high grade cherry shrimp on eBay which is when they started dying - it’s led me to believe that they might have carried some bacteria although there are still 5 of them alive and I made sure to acclimate them without introducing the water they came in. 
 

Shrimp Type? Neo caridina 

Shrimp Amount? 50-60

Shrimp Source? Local fish shop + a batch of 10 Cherry on eBay 

Tank Size? 54l

Water Source? Tap water dosed with prime and dropped back in to tank at a steady rate. 

Temperature? 24

PH? 7

GH? 120-180

KH? 120

Ammonia? 0

TDS ? 330

Feeding Type of Food And Amount? 1 blood worm cube every few days 

Do you use CO2? No 

I’ve noticed some of them have a almost black/ translucent patch on them when they die although it doesn’t look too out of place - I will try and get a picture of this. 
 

 

if anyone has any kind of idea as to what’s causing this please let me know  

 

attached is a video of one as it was dying and a picture of my tank after feeding - they show no signs of lethargy and are active. From my eyes they look healthy but maybe you can see something else. 

[Jmanrow503]

I have learned to be very careful about buying livestock on eBay. Make sure it is a well-established company, with good reviews. I would also feed shrimp pellets which offer a better balanced nutrition. I am sticking to established, well-known USA shrimp breeders, as I have heard of some populations of imported shrimp mean infected or infested with diseases of various sorts.

I am new to this group, and I'm not sure what the policy is about posting any links to shrimp breeders.