Dutch Masters is a company that makes different products that many MJ growers use.
I will link you to a page or two of mine that I need to update, but you can get an idea of some of my stuff, but I will post back in a minute with the links. In the mean while here is a link that will show how to use the GH 3 part in order to maxamise your growing IMO, http://boards.cannabis.com/showthread.php?t=93676
It may seem confusing at first, but just ask any questions and read some of the questions that are posted throughout the thread and I think that you will get enough info to be able to ask some questions to get you on the right track.
Adieu