Aquatic Nature Co2 Pro Tank

i have just bought the pro kit but at the moment i am just starting with one plant to see if the seeds would sprout..the thing is the place is not ready yet but this plant is not going very well in its life as it looks like nute burns..ive tried the cheap method but ph didnt go down (in the aerogarden) and now ive flushed it with distilled water and put it into a hydro pot (the new leaves grew with a good green colour but look droopy maybe the flushing had to do with it? any suggestions?
you think its best to use the co2 tank now to get the ph down? or should i wait to see if the flushing of the water work? and also is the diffuser supposed to go into the water or in front of a fan? would it be bad for the res tank?

Uhh.... Roots don't need supplemental CO2. Actually, I don't believe roots use CO2 at all! I'd place the 'diffusor' in front of a fan or above the plants, outside of the reservoir.