Mother nature should have turned the switch to flowering by now so you should be noticing something. Are you sure there isn't a light source at night such as a street light, neighbors security light or something that might disrupt the night cycle? If they were males I'd be willing to be they would have shown now as male plants typically show before females and sometimes will show without a change in light. At your latitude you should be around 11 1/2 hours of darkness which should be enough for flowering.

If possible try covering them around 6 p/m every evening for a few weeks and increase the darkness to about 12 1/2 -13 hours.