It's tempting to take shortcuts when you have a hydroponic gardening garden. It doesn't matter how much experience you have with hydroponics. However, it is important to remember that improperly making hydroponic nutrients can negatively impact plant performance. 

This is especially important for mixing hydroponic nutrients, such as two-parts or three-parts. These can be more complicated than most growers realize.

These are some tips and guidelines to mix multi-part hydroponic nutrients.

Do not combine concentrated hydroponic nutrients with very little water.

For a specific reason, two- and three-part nutrients can be separated into separate "parts". A white precipitate can form if the "parts' are mixed while they are still concentrated or in very small amounts of water. Depending on the nutrients' composition, this can occur in 60 seconds. 

A or B should be first?

The first part that contains phosphate should be added. The order in which the nutrient parts are added can have an impact on the stability of the solution, particularly if the water contains high levels of alkaline. 

Alkalinity (carbonate or bicarbonate), is a component in natural water that causes high pH levels. The stability of certain nutrient species such as iron, calcium, and zinc, as well as copper, sulfate, and manganese, will be significantly reduced by adding nutrient doses to high-alkalinity water.

It's better to add the part that will most lower the water pH than trying to adjust the pH level before you do anything. This is usually the part that contains phosphate. This is often Part B in 2-part nutrients. Part B is therefore preceding Part A.