You don't need flowering nutes until it starts to really bud, not during or before the transition. A couple weeks into the flowering is what I do, but many do it at the change or a week after. It won't actually hurt changing early, and you won't see a difference really either way unless you compare side x side crops. You don't need to do any water break inbetween unless you think they're already too hot with nutes.
What pot size are these in and how big? You say you have vegged for 6 weeks, that's a very long time and they should be pretty damn huge... You should be in the 2-5 gallon container range depending on how well it's gone. If you do need to transplant you must do it right now at least a week or two before flowering and just because that might add a little time doesn't mean you can skip it. Plants that old could be rootbound beyond all belief, probably are. You cannot transplant effectively during flower, they stop most all root growth and it's pointlessly too late then and either does nothing to help growth that late or shocks them and takes away from your yield. Dont' do it.
