Here is an off the cuff over view of how 3 part is interpreted. Flora 3 part consist of Micro/m Grow/G
and Bloom/B. When using the 3 part, you must always premix in water and the Micro must always be applied to the water first because of the ionic make up of it and if not mixed in the proper order you may encounter a nute lock up. So as a basic rule, you want to mix M, G, and then B. 2-4-2 or any such numbers will generally be in the mixing order of 2/micro 4/grow and 2/bloom these numbers are just an example. when you see the numbers 5-5-5 it means 5ML of each of the parts to a gallon. Example you are going to make 10 gallons of water at 5-5-5 you would have 5ML of say grow for each gallon giving you a total of 50ML of grow for a 10 gallon bucket and the same would be the case for Micro and Bloom. Remember 5ML is just one teaspoon too, so in this case it would be 10 teaspoons of all 3 parts starting off the mix with Micro.
The nutes you are using are nice as well. The GH 3part is just a reliable, efficient, stable and cost affective way to go and when done right you can have excellent results with no additives IMO.
Hope this helps some.
Adieu