It's the length of the night that triggers them to flower. You started them too early for that strain. {the shorter season strains have to be put out later} You can keep them from early flower by putting a light on them early morning or late afternoon to make the "day" a little longer, or you can break the night up into two parts by turning on the light for an hour at midnight. Either one will keep the plant in veg until the daylight gets long enough naturally.
Or you can just start a little later. I got going in early March in NW Florida, and I ran into all sorts of early flower problems. Wasted some of my Bag Seed Tester #1 {Hurricane Head} seeds in the process.