Im new to the board but wish to add what I have found...
You will be mixing high medium and low nitrogen loving plants.
Lettuce may turn out bitter with too much nitrogen and tomatoes will produce less with less nitrogen or become deficient.
Many herbs need a 5.5 ph and tomatoes are a 6.2 to 6.5.
The Offspring would say ------ You Goto Keep Em Separated
This link has some good info for you…
Hydroponic Basics from Shamanshop.net.