how long is the tank running?
Do you have in this tank fish or other shrimps?
In the past when i had planted tank with co2 , i have the same result as you, i killed around 30 amanos ... in one day,,,
Its beter to close the co2 for one two days add the shrimps and the open again the co2.
i believe you do an aclimation for srhimps for 1-2 hours , drop by drop ....