Are you planning to only automate macronutrients (or micronutrients)? Or do you have another dosing pump?
I assume you are aware you cannot mix the two together and dose them at the same time.
In general, the chemicals will not precipitate out, unless you make them very concentrated.
As long as the containers are well sealed, then you shouldn't run into any issues with air contamination either.
As for light contamination, you can just wrap the bottles in construction paper or something similar.