Cardinal Dennerli Shrimps Dying ?!

[Jehadkh]

Hello everyone im not new in the shrimps hobby and breeding shrimps i got 3 tanks with neocaridina and 3 tanks with caridina and tigers galaxies tibee amanos almost everything and all is doing fine except caridinals now my problem is that i got a new tank from 2 weeks with cardinal shrimps like 15 shrimp from local breeder and they start dying like each two days i found one is dead still like 4 of them left now ,

"Before one year in the start i kept cardinals for 3 months in tap water and they breed normally but the tank cracked and everything in it is gone"

Today im more in this hobby and using Ro/di water and i think im in the next level but lts talk about the tank parameters

Reminerals salt : Dennerle Sulawesi Gh+/Kh+

Now the Water prameter is :
Tank volume is 60L

pH 7.6 - 8.0
Ammonia : 0
Nitrite : 0
Nitrate : 20-30 its a little high i know
GH : 8
Kh : 5
Tds : 240
Temp : 29C

Tank mates : 7 Rabbit snails , 10 orange sunkist shrimps "Neos"

Substrate : Seachem Flourite Black + Ceramic Media Underneath covered with the soil

Filter : Pat Mini Aquael Already Cycled with the help of another filter

With some rocks and Floating plants and java fern

I think that the parameter is good to enough to keep them alive any suggestions maybe the tank is big for them or flow is high or im doing something wrong ?

something to say and i think its important ,
I know that the anntenas of the cardinal shrimps is longer than others small shrimps but the cardinals i have now they got very short antennas maybe thats the reason they are dying ?

Almost all the time they are steady not grazing or moving they prefeer to hide and standstill

Really need advices and suggestions

Any questions or missing info ill reply and provide more pic if needed

Thnx