A little uncertain as to nutrient adding

Wassup all, this might be a dumb question...but this is my first grow so just trying to keep it all straight. I have a aeroponic setup, and I was a little uncertain as to when the water level drops, should I add regular tap/distilled water (does it make a diff?) and add nutrient mixed water occasionally? Or do I make a nutrient water mix (using floraduo a&b) every time it needs water?

top up with water.there are ways to tell if nutes are needed without an ec meter by ph swing,plant appearence,wether you do a res change every 2 wks or not,lighting used (stronger lights more nute/water uptake),etc etc.
use the search or google:res ppm or res addback or aeroponic ph drift etc etc

top it up with the same solution you already had in the system (nutes and ph mix)