Hydroponic Lettuce Fertilizer 24-15-36

[e_deher]

I am new to hydroponics and am in the process of starting a small DWC system at home. I ordered some rockwell cubes, net cups, airetor with stone, and some hydroponic fertilizer i found on amazon. It claims to be 24-15-36 and costs about 16 bucks for 2 pounds which can yield 160 gallons of solution. The numbers seem relatively good and i was planning to use this fertilizer straight as is. I am going to start off with leafy greens in the beginning such as lettuce and spinach and maybe graduate to tomatoes and some berries later on if it works well. So my question is: since this is a lettuce intended fertilizer, would it work with tomatoes and strawberries as well or should i be looking at a bloom fertilizer? Also, do i really have to replace the water every week or can i just top it off as needed?