Do you have artificial light on them in the off-sun hours?
If they will not be going outdoors for the season, put them on an 18 hours on, 6 hours off (18/6), 20/4 or 24/0 cycle.
If they will be going outside, give them 15 hours of light, and 9 hours of darkness per day.
Anything lower than 15 hours (or there about), they will flower. The only reason for the shorter lights-on for plants that go outdoors, is because that's pretty well what the sun will be available to the plants when they go out side. If the plants get too many hours of light a day before they go out, the sudden drop in that few hours of availability will cause the plants to flower, then reveg, then flower again in the fall.
Does that make any sense?
PS. I'm from Toronto. Much of my family lives there. Too bad for the damned Leafs. This was their year!