I dont like to mess with them in flower so if you have to do it do it now. Stress them during flower and you run the risk of a herme, if you break some polen sacs around the others you might screw your whole crop. If you must do it now before flower starts with light cycle. FYI I put them in the final pots at three inches. It slows the growth becasue the roots grow instead of the plant but by the time they are your plants size, basketball, I put them in flower and the root system is giant and they flower great.