What size room have you got, fans, extraction, what size were they when you flipped? What strain are you growing? We need this info before we can help.
I got 19oz crispy bone dry bubblegum off a 600w with 4plants in a 1.2 x1.2 this could of still been improved on, but this means nothing unless i told you that I grew in coco/perlite and biobiz mix (60/20/20) in 11ltr square pots, i vegged for about 8weeks under 600w, topping, supercropping and training, i also took around 150 cuttings from these monsters, they were around 5foot when flipped and finished just under 6. These were were also lollipopped and slightly defoliated throughout. I used canna a and b throughout, with cannazyme, pk, big bud, bud candy, carboload and ripen, its not my grow diary so wont go to indepth!
Ive now got 8 in the same space but only expecting around 2oz off each plant because they were flipped at around 10 inches with a bit of topping through veg to produce a scrog, originally i had 11 in there but ripped out 3 becuase 1 hermied - the 3were all the same strain grown from seed and didnt want to risk any more trannys - lesson learned though dont scrog with an unknown strain, dont put them at the back and dint put so many in there!!
Back to the point in hand though IMO It all depends how long you veg them for and under what light to determine yield, now before i get slammed for this comment of course environment, strain etc come into it but simply, the longer the veg, the bigger the plant, the bigger the yield - simples.
I typically veg for around 6/7weeks under a 125w cfl in a small cutting tent. This sounds long but by the time i put them in the flower room they will only stand around 8inches with Loads of nodes, they get reppoted into final pot but they still need vegging for at least 2wks under a 600w before i switch to let them get used to the environment change and to get their feet in their new home.
Depending on the method im trying, sog, scrog, 4plants, 1monster etc depends how long i veg before flip, as i said the last grow was vegged for 8wks but this was under a 600 i didnt count the time under the cfl which was around 4weeks. So in reality they recieved around 3mths / 12 weeks veg in total
Now you see the more info you provide the more we can help!
Im by no means an expert and everybody learns something new about this wonderfull plant everyday but without knowledge and sharing we wont truely know its full potential, all i can say is read and experiment!