Hello
With them being photoperiod you can extend the vegetative cycle as long as you want and your space will allow. If all the plants are at least 3-4 weeks old they will flower and do well. Me personally i like at least a 6 week veg time. you could do either option, flower them all now and have 2 that are a little smaller even though they would still catch up nicely, or wait a week or two and do a bit more growth and get 3 larger plants.