In my experience.. shrimp tolerate CO2.. but wont breed as much as if it were no co2.. (next tank i'm going to to a very low bubble count).
Ferts.. is a mixed bag. Some say yes some say no..
In my experience.. Adult shrimp seems to be okay but babys tend to bight the dust.. Out of my previous batch of CRS i only had 2 babies make it.. this time i decided to cut out all ferts and i count about 19.. so no more ferts in there for about a month until they grow up.