How old is it? I give my plants nothing at all (except water) for several weeks.
Once ready for food, there are as many answers as there are growers. I find GH Flora nute's easy to use, easy to find, competitively priced, and they work well.
Without knowing all the specifics, there could be any number of reasons why your last grow was so small. Most likely it was from a combination of reasons.
The size of your plant is going to depend on A LOT of different factors. Was the light strong enough, did it veg long enough, was the waters PH good, were nutrients enough, too much, or non existent, was the medium good, were the temperatures okay and stable, was humidity good, were they getting co2 and air circ. I could go on and on and on. To get a solid answer you're going to need to spend a little time and write a solid write up of your grow.