I would check with the manufacturer, some of the additives I use from the same mfg. require mixing/shaking before use, others don't.
If they are in a clear container, after 2-3 weeks, do you see any precipitation?
I use the TM balling method. I buy it in the powder form, mix it into 1g water jugs and wait a day and shake it few time again. Then I put it in my dosing containers and let the dosers run until I need to refill. The solution stays clear and I do not see any signs of solids. Hope that helps .