What are you talking about? If you didn't mix and were using 5 different nutes are you going to have 3 to 5 gallons of water for each nute in order to water just a few plants in 2 to 5 gallon pots. That means you could have 25 or more gallons of water for a few plants because you are trying to seperate all of the nutes in their own mix, LOL. Not mixing nutes, where is the thread on that? This is done in hydro, soilless and soil all of the time. Yes there are some nutes that have a particular order to be mixed in such as the GH3 part, and organic nutes with som poroxide res cleaners, but these ar a few exceptions. Not trying to be hard on anyone, but you can mix nutes together that is why there are TDS/PPM meaters in order to measure the dissolved solids or amount of nute consentrate.
Adieu