wow man, you shouldnt even be asking if you need to use anything else besides water, I mean look at your plant ( no offence ) Go to a headshop and get some organics if you dont want to use chemicals. Otherwise just run down to walmart and pick up some allpurpose miracle grow. Use like 1/3 of what it says. Make sure you ph after... even tho I really doubt you PH. If I were you though I would get a cheap ph meter.
Grow on budddy <3