LST. should help next time round or you could try sog or scrog, those big colas are stopping you getting your light nearer to the rest of the plant. A better yielding strain will also help.

I think most first time growers are disappointed with the amount of bud they get. I grow White Rhino which is a big yielder, a friend of mine who has growing pretty much locked down was able to get 12oz of good bud (White Rhino) under a 600w HPS, but he had 4 smaller plants not one big one.

Also bear in mind that a lot of people exaggerate how much they crop.