I just purchased about 30 RCS a few days ago. I have pressurized co2 and dose with ei. From what I saw on the first 2 days was that I had my co2 too high. All the shrimp were hanging on the floating plants and the rim of the tank, right at the top of the waterline. This was at the beginning of the lights off cycle. 1 or 2 shrimp died. None of them were moving or eating,just sitting there, and I couldnt figure out if it was the ferts or the co2 or copper or something else. Well I figured they needed more oxygen because they were ALL at the top of the water. I moved my outflow to create a larger "ripple" on the surface of the water and within an hour they all had gone back to their various places in the tank and were eating properly. I haven't noticed any effect on them while dosing my ferts either. It was either too much co2 (which I also turned down slightly) or not enough o2 that was bothering them and causing casualties.
Just something to look out for and is only based on my limited experience with cherry shrimp.
Good luck!
-Mike B-