nullis nails it yet again. he does have a point about the internet, but we all know its easier to just post and wait... and between nullis and a few other pros here you will surely get the right answer. get some molasses bro, its cheap. it also mixes with room temp water better than brown sugar. the brown sugar won't hurt, unless you over do it. But honestly, nullis and i and many others have grown killer herbs without added carb sources. it has to do with what is in your media and what nutes you use.
so: what media? what nutes?
peace.