Heh, it never clicked in my head up to this moment, but I can easily get the data on my water composition (a friend has a brewery and we share the water supply) and I also have some of my brewing supplies for treating the water to get it to the right composition for beer so I'll just have to have a play with the numbers.
This was the first year I grew hydroponically and the plan was to mix my own, but then I needed something quickly and the miracle gro seemed to work so I just stuck with it. For the next season I will mix it myself.

Thank you!