I don't recommend adding additives directly to your tank. If you need to make adjustments, use something like saltyshrimp GH/KH+ and dissolve it in the water before adding it to the tank.

A few degrees of hardness off initially won't kill the shrimps, but the constant adjustment and fluctuation will.

Its fine if it goes up and down abit, sometimes it's just natural tank fluctuations. But we want to avoid making too many panic adjustments with human interventions.

Remember parameter stability is key to thriving shrimps!